Add debug support in Test Explorer

[mnoah1]

Add debug support to the test explorer.

When this feature is enabled (via bazelbsp.debug.enabled setting), an additional debug run option will appear on each test item.

Overall flow:

• When a debug button for a test case is clicked, run is trigged as usual, with added additionalBazelParams (now supported by bazel-bsp server). These flags are configurable based on bazelbsp.debug.bazelFlags and should include any flags needed to get Bazel to build and launch the target in debug mode.
• As the build runs, messages are watched for a debug ready message. The pattern to watch for is configurable in bazelbsp.debug.readyPattern.
• Finally, once the pattern is matched, the VS Code launch configuration is triggered. This allows use of an existing launch configuration in the workspace (which can be set via settings, workspace, launch.json, etc), configurable via bazelbsp.debug.launchConfigName.

If any of the settings are not properly set, the run will still attempt to proceed but print a warning in the output.

[shuklahy]

LGTM