Convert Tileset into a MutableMapping #1402

Job	Run time
sdist	50s
ruff	6s
mypy	25s
parse_sdl (windows-latest, 3.2.16)	47s
parse_sdl (macos-latest, 3.2.16)	33s
pyodide	33s
build-macos (cp314t-*_universal2)	43s
tox (ubuntu-latest)	33s
test-docs	33s
build-macos (pp310-*)	43s
linux-wheels (x86_64, cp314t-manylinux*)	40s
build-macos (cp310-*_universal2)	40s
linux-wheels (aarch64, pp310-manylinux*)	38s
linux-wheels (x86_64, cp310-manylinux*)	41s
linux-wheels (x86_64, pp310-manylinux*)	40s
linux-wheels (aarch64, cp310-manylinux*)	16s
build (windows-latest, pypy-3.10, x64)	42s
build (ubuntu-latest, 3.14t, x64)	1s
linux-wheels (aarch64, cp314t-manylinux*)	1s
build (ubuntu-latest, 3.10, x64)	29s
build (windows-latest, 3.10, x64)	39s
build (windows-latest, 3.14t, x64)	31s
build (windows-11-arm, 3.11, arm64)	41s
build (windows-latest, 3.14t, x86)	31s
build (windows-11-arm, 3.14t, arm64)	1s
build (ubuntu-latest, pypy-3.10, x64)	33s
build (windows-latest, 3.10, x86)	31s
publish	1s
	14m 2s

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