[Alok Pandey (alok-108)]

Fixes #3340

Problem

ImplToApiMapping.wrap_handler() cached wrappers by mutating _pw_impl_instance_* attributes onto handler or handler.__self__ via setattr(). This raised AttributeError when registering:

• built-in functions and bound methods (list.append, print, len, set.__contains__, re.Pattern.match)
• C method-wrapper objects (str.__eq__)
• __slots__ / @dataclass(slots=True) bound methods and callable instances
• @dataclass(frozen=True) bound methods and callable instances

Solution

• Cache wrapped handlers per ImplToApiMapping instance in a weakref.WeakValueDictionary instead of setting _pw_impl_instance_* attributes on user objects.
• Key Python bound methods (inspect.ismethod) and built-in/C bound methods (BuiltinFunctionType / MethodWrapperType with __self__) by receiver identity (id(__self__)) and underlying function/qualname metadata so repeated attribute lookups (messages.append, allowed.__contains__, collector.handle) return the identical wrapper for remove_listener() / unroute(), while keeping distinct instances isolated and preventing reference-cycle leaks.
• Fall back to id(handler) for standalone functions, lambdas, callable instances (including unhashable slotted/frozen callables), and mocks (MagicMock).
• Add sync and async regression tests in tests/sync/python/test_handlers.py and tests/async/python/test_handlers.py.

Verification

• SKIP=pyright pre-commit run --files playwright/_impl/_impl_to_api_mapping.py tests/sync/python/test_handlers.py tests/async/python/test_handlers.py: all checked hooks passed (black, mypy, flake8, isort, Check License Header, AST/whitespace checks; pyright run separately below)
• npx --yes pyright@1.1.403 playwright/_impl/_impl_to_api_mapping.py tests/sync/python/test_handlers.py tests/async/python/test_handlers.py: 0 errors, 0 warnings, 0 informations
• mypy --platform linux playwright: Success: no issues found in 105 source files
• python scripts/check_test_registry.py: passed
• PW_CHECK_PROTOCOL=1 pytest tests/sync/python/ tests/sync/page/test_page_route.py tests/sync/page/test_page_event_console.py tests/sync/page/test_page_expose_function.py --browser=chromium: 136 passed, 4 skipped (3 Windows SIGALRM, 1 WebKit-only), 1 xfailed
• PW_CHECK_PROTOCOL=1 pytest tests/async/python/test_handlers.py tests/async/python/test_listeners.py tests/async/python/test_console.py tests/async/python/test_issues.py tests/async/python/test_asyncio.py tests/async/page/test_page_route.py tests/async/page/test_page_event_console.py tests/async/page/test_page_expose_function.py --browser=chromium: 109 passed, 2 skipped (1 Python 3.14 PEP 649, 1 WebKit-only), 1 xfailed
• PW_CHECK_PROTOCOL=1 pytest tests/common/ --browser=chromium: 2 passed, 2 skipped (Windows SIGINT)

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