[ty] normalize typevar bounds/constraints in cycles

[carljm]

Fixes astral-sh/ty#1587

Summary

Perform cycle normalization on typevar bounds and constraints (similar to how it was already done for typevar defaults) in order to ensure convergence in cyclic cases.

There might be another fix here that could avoid the cycle in many more cases, where we don't eagerly evaluate typevar bounds/constraints on explicit specialization, but just accept the given specialization and later evaluate to see whether we need to emit a diagnostic on it. But the current fix here is sufficient to solve the problem and matches the patterns we use to ensure cycle convergence elsewhere, so it seems good for now; left a TODO for the other idea.

This fix is sufficient to make us not panic, but not sufficient to get the semantics fully correct; see the TODOs in the tests. I have ideas for fixing that as well, but it seems worth at least getting this in to fix the panic.

Test Plan

Test that previously panicked now does not.

[astral-sh-bot]

Diagnostic diff on typing conformance tests

No changes detected when running ty on typing conformance tests ✅

[astral-sh-bot]

mypy_primer results

Changes were detected when running on open source projects

beartype (https://github.com/beartype/beartype)
- beartype/claw/_package/clawpkgtrie.py:66:29: warning[unsupported-base] Unsupported class base with type `<class 'dict[str, PackagesTrieBlacklist]'> | <class 'dict[str, Divergent]'>`
- beartype/claw/_package/clawpkgtrie.py:247:29: warning[unsupported-base] Unsupported class base with type `<class 'dict[str, PackagesTrieWhitelist]'> | <class 'dict[str, Divergent]'>`
- Found 494 diagnostics
+ Found 492 diagnostics

scikit-build-core (https://github.com/scikit-build/scikit-build-core)
- src/scikit_build_core/_logging.py:153:13: warning[unsupported-base] Unsupported class base with type `<class 'Mapping[str, Style]'> | <class 'Mapping[str, Divergent]'>`
- Found 39 diagnostics
+ Found 38 diagnostics

dd-trace-py (https://github.com/DataDog/dd-trace-py)
+ ddtrace/testing/internal/test_data.py:140:15: warning[unsupported-base] Unsupported class base with type `<class 'TestItem[Test, Never]'> | <class 'TestItem[Unknown, Unknown]'>`
- Found 8325 diagnostics
+ Found 8326 diagnostics

rotki (https://github.com/rotki/rotki)
- rotkehlchen/accounting/structures/processed_event.py:85:75: warning[unused-ignore-comment] Unused blanket `type: ignore` directive
- rotkehlchen/api/rest.py:1041:73: warning[unused-ignore-comment] Unused blanket `type: ignore` directive
- Found 2052 diagnostics
+ Found 2050 diagnostics

pandas-stubs (https://github.com/pandas-dev/pandas-stubs)
- pandas-stubs/_typing.pyi:1209:16: warning[unused-ignore-comment] Unused blanket `type: ignore` directive
- Found 5514 diagnostics
+ Found 5513 diagnostics

No memory usage changes detected ✅

[dcreager]

👍 to landing this separately from any follow-on work