Summary

This PR updates the StringLike::FString variant to use ExprFString instead of FStringLiteralElement.

For context, the reason it used FStringLiteralElement is that the node is actually the string part of an f-string ("foo" in f"foo{x}"). But, this is inconsistent with other variants where the captured value is the entire string.

This is also problematic w.r.t. implicitly concatenated strings. Any rules which work with StringLike::FString doesn't account for the string part in an implicitly concatenated f-strings. For example, we don't flag confusable character in the first part of "𝐁ad" f"𝐁ad string", but only the second part (https://play.ruff.rs/16071c4c-a1dd-4920-b56f-e2ce2f69c843).

Update PYI053

This is included in this PR because otherwise it requires a temporary workaround to be compatible with the old logic.

This PR also updates the PYI053 (string-or-bytes-too-long) rule for f-string to consider all the visible characters in a f-string, including the ones which are implicitly concatenated. This is consistent with implicitly concatenated strings and bytes.

For example,

def foo(
	# We count all the characters here
    arg1: str = '51 character ' 'stringgggggggggggggggggggggggggggggggg',
	# But not here because of the `{x}` replacement field which _breaks_ them up into two chunks
    arg2: str = f'51 character {x} stringgggggggggggggggggggggggggggggggggggggggggggg',
) -> None: ...

This PR fixes it to consider all visible characters inside an f-string which includes expressions as well.

fixes: #10310
fixes: #10307

Test Plan

Add new test cases and update the snapshots.

Review

To facilitate the review process, the change have been split into two commits: one which has the code change while the other has the test cases and updated snapshots.