Allow running tests from Navigator

### Description

# Running tests in a big project requires too many clicks in some cases.

Scenario: You have multiple files open, some of which are test classes.
If you want to run a specific test, you often end up in doing the following:

* in the editor tab, search te required file
* in navigator select the required test method
* in left gutter select the green arrow to run or debug the test

even in the case that the editor tab already points at the required test file.

### Use case/motivation

I would like to be able to (re)run a specific inside a test class by clicking on it in the navigator, when that test class has focus.

### Related issues

No.

### Are you willing to submit a pull request?

Yes

The issue names no files or tests; start by locating Navigator handling for test classes and methods, then trace the existing gutter run/debug action. Done means selecting a specific test method in Navigator while its class has focus can run or debug that test without switching to the editor tab.

Written by the indexing model from the issue text.