Distinguish booleans from strings in uniqueItems

[muneikh]

uniqueItems normalizes booleans using str(), making true collide with the JSON string "True" (and false with "False"). Valid arrays such as [true, "True"] therefore fail validation. The same collision occurs inside nested arrays and objects.

Use a type-tagged boolean value in the existing normalization function. This keeps booleans distinct from strings and numbers while equal boolean values still compare equal. Regression tests cover both booleans, nested arrays/objects, and numeric distinction controls under drafts 04, 06 and 07.

Validation: 18 new cases fail before the change; the complete non-benchmark suite passes after it (625 passed, 4 skipped, 12 deselected) on Python 3.13. Pylint 4.1 reports the same nine diagnostics and 9.90/10 score as an untouched checkout; git diff --check passes.