fix(node:os): add priority methods

[andrewtdiz]

Summary

• add node:os getPriority/setPriority runtime helpers backed by platform priority calls
• validate Int32/range arguments and surface Node-shaped priority errors
• route priority methods through HIR, native dispatch table, and captured-method dispatch

Verification

• cargo fmt --all --check
• cargo check -p perry-runtime -p perry-hir -p perry-codegen
• ./scripts/check_file_size.sh
• ./scripts/regen_api_docs.sh
• ./run_parity_tests.sh --suite node-suite --module os --filter priority
• ./run_parity_tests.sh --suite node-suite --module os --filter methods

[andrewtdiz]

Superseded by #1922, rebased on current main after #1890 landed.