Support subclass inits for `Url` and `MultiHostUrl` #5267

Job	Run time
coverage	3m 8s
test on ubuntu	2m 6s
test on macos	1m 46s
test on windows	4m 42s
lint	1m 11s
rust benchmarks	3m 16s
test-debug 3.13	1m 11s
test MSRV	2m 45s
test-debug pypy3.10	1m 24s
test-pydantic-integration	2m 27s
test 3.8	2m 0s
build on ${{ matrix.os }} (${{ matrix.target }} - ${{ matrix.interpreter \|\| 'all' }}${{ (((matrix.os == 'linux') && format(' - {0}', (((matrix.manylinux == 'auto') && 'manylinux') \|\| matrix.manylinux))) \|\| '') }})	0s
test 3.9	2m 16s
test 3.10	1m 57s
test 3.11	1m 49s
test 3.12	2m 15s
build pgo-optimized on ${{ matrix.os }} / ${{ matrix.interpreter }}	0s
test 3.13	1m 46s
test pypy3.9	2m 13s
test pypy3.10	2m 18s
build sdist	25s
build-wasm-emscripten	2m 42s
test build on ${{ matrix.target }}-${{ matrix.distro }}	0s
test build on ${{ matrix.os }}	0s
inspect-pypi-assets	0s
check	1s
release	0s
	43m 38s

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