Make test explorer functionality optional

I see that new functionality for the test explorer has been added to display coverage. Can this functionality be placed behind a setting? We use this Bazel extension primarily for build file syntax highlighting, but are using a different solution for test case execution to better work with our large monorepo setup, and it can result in user confusion when there are too many extensions contributing to the test explorer. Other extensions that contribute to test explorer typically offer either a way to opt out of this functionality via a setting (e.g. Python, Go, etc), or package this functionality in a separate test runner extension (e.g. Java).

No file or test is named. Start by locating the extension's test explorer coverage contribution and its configuration declarations, then review how comparable opt-out settings are represented. Done means a user setting can disable that contribution without affecting Bazel syntax highlighting, with the coverage behavior checked.

Written by the indexing model from the issue text.