build

settings: own StackedConfig by UserSettings, migrate tests to use config layer #16733

Job	Run time
build (ubuntu-latest)	5m 13s
Build jj-lib without Git support	48s
build (macos-13)	7m 43s
Check protos	33s
build (macos-14)	4m 4s
build (windows-latest)	10m 11s
Check that MkDocs can build the docs	10s
Check that MkDocs can build the docs with latest Python and uv	11s
build (ubuntu-latest, --all-features)	6m 19s
Check formatting	17s
Clippy check	2m 35s
cargo-deny (advisories)	27s
cargo-deny (bans licenses sources)	22s
	38m 53s

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