build_test rule kind is _empty_test, which seems off when trying to filter. Would it be okey to rename to skylib_build_test?

Hi 👋

The macro [build_test](https://github.com/bazelbuild/bazel-skylib/blob/main/rules/build_test.bzl) uses the rule `_empty_test` under the hood.

Such name for a rule is cryptic when trying to filter targets by kind:

```
bazelisk query 'kind(_empty_test, //...)'
```

What do you think, is there a chance to rename `_empty_test` to something more user-friendly, such as `skylib_build_test`?

Start with rules/build_test.bzl and inspect how the build_test macro defines and exposes the _empty_test rule. Run the documented Bazel query to confirm the current kind, then verify that renaming the rule produces the proposed user-friendly kind while build_test behavior remains unchanged.

Written by the indexing model from the issue text.