[ty] Handle dynamic classes in string annotations

[charliermarsh]

Summary

Previously, creating a dynamic class inside a string annotation could panic because the call's AST node belongs to a separately parsed annotation rather than the enclosing module:

from types import new_class
from typing import Annotated


def example(
    first: "Annotated[int, type('First', (), {})]",
    second: "Annotated[int, new_class('Second', ())]",
) -> None: ...

Dynamic classes normally retain a scope-relative AST node index as their identity. For calls parsed from string annotations, that index was missing or later resolved against the wrong AST.

We now anchor those calls to the enclosing string expression and record the call's relative source range. This preserves distinct class identities, points diagnostics at the actual call, and handles nested annotations without retaining absolute source positions.

Supersedes #27851.

[astral-sh-bot]

Typing conformance results

No changes detected ✅

Current numbers

The percentage of diagnostics emitted that were expected errors held steady at 97.68%. The percentage of expected errors that received a diagnostic held steady at 93.44%. The number of fully passing files held steady at 109/136.

[astral-sh-bot]

Memory usage report

Memory usage unchanged ✅

[astral-sh-bot]

ecosystem-analyzer results

No diagnostic changes detected ✅

Flaky changes detected. This PR summary excludes flaky changes; see the HTML report for details.

Full report with detailed diff (timing results)