…nd endpoint_configuration vpc_endpoint_ids handling with OpenAPI specification import (body argument)

Reference: #13841

Before code updates, these new acceptance tests show how the Terraform configuration value would not be applied if an OpenAPI specification was imported:

```
=== CONT  TestAccAWSAPIGatewayRestApi_DisableExecuteApiEndpoint_OverrideBody
    resource_aws_api_gateway_rest_api_test.go:847: Step 1/4 error: Check failed: 1 error occurred:
        	* Check 2/2 error: aws_api_gateway_rest_api.test: Attribute 'disable_execute_api_endpoint' expected "false", got "true"

--- FAIL: TestAccAWSAPIGatewayRestApi_DisableExecuteApiEndpoint_OverrideBody (10.30s)

=== CONT  TestAccAWSAPIGatewayRestApi_EndpointConfiguration_VpcEndpointIds_OverrideBody
    resource_aws_api_gateway_rest_api_test.go:369: Step 1/2 error: After applying this test step and performing a `terraform refresh`, the plan was not empty.
        stdout

        An execution plan has been generated and is shown below.
        Resource actions are indicated with the following symbols:
          ~ update in-place

        Terraform will perform the following actions:

          # aws_api_gateway_rest_api.test will be updated in-place
          ~ resource "aws_api_gateway_rest_api" "test" {
                id                           = "m9ajz6izjl"
                name                         = "tf-acc-test-6139822644948363723"
                tags                         = {}
                # (9 unchanged attributes hidden)

              ~ endpoint_configuration {
                  ~ vpc_endpoint_ids = [
                      + "vpce-0ba0b61be45886a6f",
                      - "vpce-0ee1a2ccd6af8f011",
                    ]
                    # (1 unchanged attribute hidden)
                }
            }

        Plan: 0 to add, 1 to change, 0 to destroy.
--- FAIL: TestAccAWSAPIGatewayRestApi_EndpointConfiguration_VpcEndpointIds_OverrideBody (190.95s)
```

Before code updates, these new acceptance tests show how the Terraform resource would report an unexpected difference for missing configurations that were imported by the OpenAPI specification:

```
=== CONT  TestAccAWSAPIGatewayRestApi_DisableExecuteApiEndpoint_SetByBody
    resource_aws_api_gateway_rest_api_test.go:890: Step 1/2 error: After applying this test step, the plan was not empty.
        stdout:

        An execution plan has been generated and is shown below.
        Resource actions are indicated with the following symbols:
          ~ update in-place

        Terraform will perform the following actions:

          # aws_api_gateway_rest_api.test will be updated in-place
          ~ resource "aws_api_gateway_rest_api" "test" {
              ~ disable_execute_api_endpoint = true -> false
                id                           = "c2t6iky152"
                name                         = "tf-acc-test-8877194198775672292"
                # (8 unchanged attributes hidden)

                # (1 unchanged block hidden)
            }

        Plan: 0 to add, 1 to change, 0 to destroy.
--- FAIL: TestAccAWSAPIGatewayRestApi_DisableExecuteApiEndpoint_SetByBody (11.03s)

=== CONT  TestAccAWSAPIGatewayRestApi_EndpointConfiguration_VpcEndpointIds_SetByBody
    resource_aws_api_gateway_rest_api_test.go:415: Step 1/2 error: After applying this test step, the plan was not empty.
        stdout:

        An execution plan has been generated and is shown below.
        Resource actions are indicated with the following symbols:
          ~ update in-place

        Terraform will perform the following actions:

          # aws_api_gateway_rest_api.test will be updated in-place
          ~ resource "aws_api_gateway_rest_api" "test" {
                id                           = "adeg2zcky2"
                name                         = "tf-acc-test-7848512816247428885"
                # (9 unchanged attributes hidden)

              ~ endpoint_configuration {
                  ~ vpc_endpoint_ids = [
                      - "vpce-0653ca468e4c6ba4a",
                    ]
                    # (1 unchanged attribute hidden)
                }
            }

        Plan: 0 to add, 1 to change, 0 to destroy.
--- FAIL: TestAccAWSAPIGatewayRestApi_EndpointConfiguration_VpcEndpointIds_SetByBody (150.67s)
```

Output from acceptance testing:

```
--- PASS: TestAccAWSAPIGatewayRestApi_ApiKeySource (30.53s)
--- PASS: TestAccAWSAPIGatewayRestApi_ApiKeySource_OverrideBody (37.78s)
--- PASS: TestAccAWSAPIGatewayRestApi_ApiKeySource_SetByBody (15.25s)
--- PASS: TestAccAWSAPIGatewayRestApi_basic (669.92s)
--- PASS: TestAccAWSAPIGatewayRestApi_BinaryMediaTypes (34.56s)
--- PASS: TestAccAWSAPIGatewayRestApi_BinaryMediaTypes_OverrideBody (34.23s)
--- PASS: TestAccAWSAPIGatewayRestApi_BinaryMediaTypes_SetByBody (514.96s)
--- PASS: TestAccAWSAPIGatewayRestApi_Body (38.01s)
--- PASS: TestAccAWSAPIGatewayRestApi_Description (23.87s)
--- PASS: TestAccAWSAPIGatewayRestApi_Description_OverrideBody (60.58s)
--- PASS: TestAccAWSAPIGatewayRestApi_Description_SetByBody (92.79s)
--- PASS: TestAccAWSAPIGatewayRestApi_DisableExecuteApiEndpoint (3442.94s)
--- PASS: TestAccAWSAPIGatewayRestApi_DisableExecuteApiEndpoint_OverrideBody (2292.47s)
--- PASS: TestAccAWSAPIGatewayRestApi_DisableExecuteApiEndpoint_SetByBody (1083.96s)
--- PASS: TestAccAWSAPIGatewayRestApi_disappears (529.45s)
--- PASS: TestAccAWSAPIGatewayRestApi_EndpointConfiguration (1034.47s)
--- PASS: TestAccAWSAPIGatewayRestApi_EndpointConfiguration_Private (15.42s)
--- PASS: TestAccAWSAPIGatewayRestApi_EndpointConfiguration_VpcEndpointIds (330.11s)
--- PASS: TestAccAWSAPIGatewayRestApi_EndpointConfiguration_VpcEndpointIds_OverrideBody (205.73s)
--- PASS: TestAccAWSAPIGatewayRestApi_EndpointConfiguration_VpcEndpointIds_SetByBody (159.85s)
--- PASS: TestAccAWSAPIGatewayRestApi_MinimumCompressionSize (39.32s)
--- PASS: TestAccAWSAPIGatewayRestApi_MinimumCompressionSize_OverrideBody (1278.64s)
--- PASS: TestAccAWSAPIGatewayRestApi_MinimumCompressionSize_SetByBody (753.00s)
--- PASS: TestAccAWSAPIGatewayRestApi_Name_OverrideBody (2212.45s)
--- PASS: TestAccAWSAPIGatewayRestApi_Parameters (948.67s)
--- PASS: TestAccAWSAPIGatewayRestApi_Policy (28.00s)
--- PASS: TestAccAWSAPIGatewayRestApi_Policy_OverrideBody (80.78s)
--- PASS: TestAccAWSAPIGatewayRestApi_Policy_SetByBody (1967.74s)
--- PASS: TestAccAWSAPIGatewayRestApi_tags (1413.12s)
```