Add support for code lens to the ruby-lsp

[vinistock]

The code lens request allows us to attach a command to a piece of code. The main use case we want to support is running and debugging tests. We can add two commands to each discovered test (run | debug).

Additionally, we can populate VS Code's test interface using the same request. By using a middleware, we can retrieve test cases discovered, populate the test interface and provide similar options to run or debug examples.

Documentation: https://microsoft.github.io/language-server-protocol/specification#textDocument_codeLens

[st0012]

Is it possible to borrow some concepts or implementations from Andy's hackday project for a quick spike?

My impression is that either using VS Code's test interface or the code lens request, the logic underneath should be pretty similar (e.g. compute test location and command). And based on that, we can get a better idea on how we can integrate debug into this, either on the server or client side.

@andyw8 @vinistock WDYT?

[vinistock]

It should be possible to borrow the code lens implementation to try it out.

In terms of the debug integration, it should just be a matter of writing a VS Code command that launches that test with the debugger. Given that RDBG exports a Task already, it should be straight forward.

[vinistock]

Closed in favour of more specific issues #1554, #584.