refactor `LookupKey` logic to reduce redundancy #5683

Job	Run time
build pgo-optimized on ${{ matrix.os }} / ${{ matrix.interpreter }}	0s
build on ${{ matrix.os }} (${{ matrix.target }} - ${{ matrix.interpreter \|\| 'all' }}${{ (((matrix.os == 'linux') && format(' - {0}', (((matrix.manylinux == 'auto') && 'manylinux') \|\| matrix.manylinux))) \|\| '') }})	0s
rust benchmarks	2m 30s
build sdist	11s
build-wasm-emscripten	2m 28s
coverage	1m 14s
lint	46s
test-debug 3.13	59s
test MSRV	2m 33s
test-debug pypy3.10	3m 8s
test on ubuntu	1m 58s
test on macos	1m 46s
test on windows	4m 51s
test-pydantic-integration	1m 7s
test 3.9	2m 8s
test 3.10	1m 53s
test 3.11	1m 48s
test 3.12	1m 42s
test 3.13	1m 40s
test 3.13t	1m 58s
test pypy3.9	4m 11s
test pypy3.10	4m 23s
test build on ${{ matrix.target }}-${{ matrix.distro }}	0s
test build on ${{ matrix.os }}	0s
inspect-pypi-assets	0s
check	3s
release	0s
	43m 17s

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