Display coverage results from `bazel coverage`

[vogelsgesang]

VS Code added support for code coverage recently (See https://github.com/microsoft/vscode/issues/123713). It probably makes sense to integrate this with bazel coverage, such that the code coverage is directly shown in the IDE

• [x] Integration with coverage tasks defined in tasks.json #366
• [x] LCOV parsing
  • [x] Function coverage #366
  • [x] Line coverage #366
  • [x] Branch coverage #389
• [x] name demangling
  • [x] Java #388
  • [x] C++ https://github.com/bazelbuild/vscode-bazel/pull/398
  • [x] Rust https://github.com/bazelbuild/vscode-bazel/pull/398
• [ ] Setting to display only boolean coverage instead of hit-counts
• [ ] Builtin commands and integration into "Bazel Build Targets" treeview