What does this implement/fix?

I have some esp8266 D1 devices which I made which have both an AHT10 and BMP025 sensor attached, but I wired these to separate i2c busses. With my own custom firmware these worked just fine, but when installing esphome and setting up the i2c busses I found that only one sensor at a time would be working.

I traced this down to the Wire.h library, which stores SDA and SCL pin assignments in global variables 🙄

This PR works around this by resetting the SDA/SCL assignments and clock frequency between every i2c read and write.

Types of changes

• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Other

Related issue or feature (if applicable):
EDIT: found an issue relating to this: esphome/issues#2558

Pull request in esphome-docs with documentation (if applicable): N/A

Test Environment

• ESP32
• ESP32 IDF
• ESP8266
• RP2040
• BK72xx
• RTL87xx

Example entry for config.yaml:

esphome:
  name: env-sensors

esp8266:
  board: nodemcuv2

# Enable logging
logger:

# Enable Home Assistant API
api:
  password: ""

ota:
  password: ""

wifi:
  ssid: !secret wifi_ssid
  password: !secret wifi_pass

  # Enable fallback hotspot (captive portal) in case wifi connection fails
  ap:
    ssid: "Fallback Hotspot"
    password: "nnnnnnnnnn"

captive_portal:
  #

external_components:
  - source:
      type: git
      url: https://github.com/LouDou/esphome
      ref: i2c-esp8266-multi-bus
    components: [i2c]

i2c:
  - id: bus_a
    sda: D2
    scl: D3
    frequency: 100kHz
    scan: false
  - id: bus_b
    sda: D5
    scl: D6
    frequency: 100kHz
    scan: false

# probably any two sensors on different busses would be able to reproduce the issue on ESP8266
sensor:
  # SDA D2, SCL D3
  # AHT10_ADDRESS_0X38
  - platform: aht10
    variant: AHT10
    i2c_id: bus_a
    address: 0x38
    temperature:
      name: "Temperature (1)"
    humidity:
      name: "Humidity"
    update_interval: 300s

  # SDA D5, SCL D6
  - platform: bmp085
    i2c_id: bus_b
    address: 0x77
    temperature:
      name: "Temperature (2)"
    pressure:
      name: "Atm. Pressure"
    update_interval: 300s

Checklist:

• The code change is tested and works locally.
• Tests have been added to verify that the new code works (under tests/ folder). - no tests exist for i2c component

If user exposed functionality or configuration variables are added/changed: N/A