rewrite-python: Unknown declaring-type for unattributed method calls + public SearchResult.found

[jkschneider]

Summary

• Two paired changes that together unblock Preconditions.check(uses_method(...), V()) gates from failing wire-side evaluation when Python sources lack receiver-type attribution (e.g. unit-test fixtures that don't import the receiver). The motivating regression: rewrite-migrate-python#54's recipe wraps were silently no-op'ing for inputs like my_array.tostring() once the wire-side HasMethod gate became active.

type_mapping

PythonTypeMapping._get_declaring_type previously returned None when Ty couldn't resolve the receiver and AST inference didn't yield a recognizable type. That left JavaType.Method._declaring_type as None for method invocations like my_array.tostring() in unattributed sources. The Python MethodMatcher.matches explicitly returns False when method_type.declaring_type is None, so the in-process UsesMethod gate fails — and on the wire path TypesInUse.hasMethodUse can't reliably match the method either.

Now _get_declaring_type returns a non-null FullyQualified in every case — falling back to the shared _UNKNOWN singleton — so HasMethod / UsesMethod precondition gates work against unattributed code. The function signature changes from Optional[JavaType.FullyQualified] to JavaType.FullyQualified to document the new invariant. The intermediate resolution paths (Ty type-id lookup, attribute chain inference) that previously returned None now fall through to the Unknown fallback rather than short-circuiting.

SearchResult.found

• Adds a public SearchResult.found(tree, description=None) static factory mirroring Java's org.openrewrite.marker.SearchResult.found. Returns a new tree carrying a fresh SearchResult marker — the canonical "different tree" sentinel that Check / CompositePrecondition interpret as the gate matching. The native rewrite/python/search/{IsSourceFile,UsesType,UsesMethod} visitors (added in rewrite-python: Preconditions.or_ / and_ / not_ for RPC recipes #7625) were already calling SearchResult.found(tree), which silently AttributeError'd at runtime because the helper didn't exist; this fixes that.

• Impact on rewrite-migrate-python#54

Locally I rebuilt rewrite-migrate-python's full test suite against this branch's editable install:

Before	After
12 failing (test_array_deprecations, test_cgi_parse_deprecations, test_html_parser_deprecations, …)	All 415 passing

• (One more recipe-level fix in ChangeMethodName works only with static methods #54 was also needed — ReplaceReTemplate was gating on uses_method but matches both method and field-access forms of re.template / re.TEMPLATE — that's a small follow-up commit on the recipe side.)

Test plan

• pytest rewrite-python/rewrite/tests/ — 1198 passed, 11 skipped
• Direct unit verification: PythonTypeMapping().method_invocation_type(ast.parse("data = my_array.tostring()").body[0].value).declaring_type is _UNKNOWN ✓
• rewrite-migrate-python full suite against an editable install — 415 passed