Feature request: INSTA_FILTER, like cargo test -- filter

[CAD97]

with similar semantics; test the filter string against the name of the snapshot, and only test it if it matches.

Minimally, this would change SnapshotAssertionContext to read INSTA_FILTER and test the name, with runtime::assert_snapshot containing an if ctx.disabled() { return } early out.

That's not super useful, though, as the only thing skipped is the snapshot comparison, and perhaps loading the old snapshot.

Where this is actually useful is with insta::glob!; if glob! can skip the execution of not-selected paths, then it's possible to test just a single execution of the glob! tests, and e.g. debug just that single snapshot test with breakpoints.

As such, it probably makes more sense to call this INSTA_GLOB_FILTER with the semantics of glob_exec building a second GlobMatcher from INSTA_GLOB_FILTER and only executing the closure if that also matches the input file.