Improve detection of executable and test targets

[Silic0nS0ldier]

The extension currently has it's own logic to determine if tests are executable and/or testable;

• Targets defined with a rule named test_suite are considered testable (can technically be incorrect if a rule with the same name is used, but very unlikely).
• Targets with a _test suffix are considered testable (this matches Bazel's documented behaviour, although in practise names like test and ActionTest are also allowed).
• All targets are considered executable, which is incorrect most of the time.

This results in invalid actions being advertised in codelens, etc.

An improvement can be made today using the query filter functions tests(...) (long available) and executables(...) (9.0.0 and 8.5.0) allow us to use Bazel's own definition of what is testable and executable.

However it is not currently possible to output multiple result sets from queries, so multiple queries would be required (3, up from 1). This has a non-negliable performance impact, especially in big workspaces.

To address the performance needs, I'm adding test and executable to the proto output in bazelbuild/bazel#27955. This approach should also simplify backward compatibility (no query change necessary, just falling back to inference when Bazel version is too low).