ci(rust): caching improvements (up to 2.8x faster builds) (#2075)

Some Rust jobs (such as
[Rust/linux](https://github.com/lancedb/lancedb/actions/runs/13019232960/job/36315830779))
take almost minutes. This can be a bit of a bottleneck.

* Two fixes to make caches more effective
* Check in `Cargo.lock` so that dependencies don't change much between
runs
      * Added a new CI job to validate we can build without a lockfile
* Altered build commands so they don't have contradictory features and
therefore don't trigger multiple builds

Sadly, I don't think there's much to be done for windows-arm64, as much
of the compile time is because the base image is so bare we need to
install the build tools ourselves.

.gitignore

@@ -9,7 +9,6 @@ venv
 .vscode
 .zed
 rust/target
-rust/Cargo.lock
 
 site
 
@@ -42,5 +41,3 @@ dist
 target
 
 **/sccache.log
-
-Cargo.lock