Add `cue_binary` rule as Bazel run target for *_tool.cue files

[folliehiyuki]

CUE has a task configuration system (similar to Makefile) using *_tool.cue files (https://cuelang.org/docs/reference/cli/cue-commands/). The invokable targets are defined as CUE objects of special tool/* packages as command: <target>: {}. Tasks then can be executed by running cue cmd <target> [args].

It would be nice to have command: <target> definitions in those files exposed as cue_binary rule I can invoke via bazel run. So:

# instead of
cd <directory_path> && cue cmd <target>

# I can do this
bazel run //<directory_path>:<target>

[folliehiyuki]

Oh! I didn't know that someone already requested the same feature at cue-lang/cue#1269 (comment)