closes #460

Previous behavior:

When updating an item with a map attribute, if you attempt to set multiple keys that are identical after removing non-word characters (\w), Electro will generate the same expression attribute name for both keys. This occurs even though the original keys are different, leading to conflicts in the update operation.

This PR introduces a new change that ensures that each key will generate a unique expression attribute name.

Previously the following operation

tasks.patch({ id: '1' }).data((attrs, ops) => {
  ops.set(attrs.map['hello world'], 1)
  ops.set(attrs.map['hello    world'], 1)
}).go()

would generate only 1 expression attribute name #helloworld. this also throws an error in dynamo because you are not allowed to update the same field multiple times in the same operation.

The new PR would create 2 expression attribute names: #helloworld and #helloworld_2.

I added tests for this as well.