copy-tracking: add `get_copy_records` to `Store` #12618

Job	Run time
Check protos	26s
Build jj-lib without Git support	46s
build (ubuntu-latest)	4m 19s
build (macos-14)	3m 41s
Check formatting	15s
build (windows-latest)	8m 51s
build (ubuntu-latest, --all-features)	5m 34s
Clippy check	2m 36s
cargo-deny (advisories)	26s
cargo-deny (bans licenses sources)	25s
Check that MkDocs can build the docs	23s
Check that MkDocs can build the docs with Poetry 1.8	23s
	28m 5s

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