Move environment manipulation completely to the Ruby object

[vinistock]

The issue in #429 got me thinking about how we also mutate the environment during activation and if we manipulating it in the client made sense.

I think all environment manipulation should be contained in the Ruby class - since we're interested in the Ruby environment after all. This PR

• moves all env related behaviour inside Ruby
• stops mutating process.env completely
• adds a few tests, limited to what we can verify without a version manager installed
• adds setup-ruby to CI, since we need some Ruby to be installed in order to check for the information

[st0012]

I try to run the tests locally but it failed like 80% of the time.

Loading development extension at /Users/hung-wulo/src/github.com/Shopify/vscode-ruby-lsp
Unexpected token � in JSON at position 0

  Telemetry
    ✔ Events are sent via the defined API
    ✔ The API object is acquired via command
  Ruby environment activation
    1) Activate fetches Ruby information when outside of Ruby LSP
    ✔ Activate fetches Ruby information when working on the Ruby LSP
  3 passing (2s)
  1 failing
  1) Ruby environment activation
       Activate fetches Ruby information when outside of Ruby LSP:
     Error: Timeout of 2000ms exceeded. For async tests and hooks, ensure "done()" is called; if returning a Promise, ensure it resolves. (/Users/hung-wulo/src/github.com/Shopify/vscode-ruby-lsp/out/test/suite/ruby.test.js)
        at listOnTimeout (node:internal/timers:559:17)
        at process.processTimers (node:internal/timers:502:7)

Error: 1 tests failed.
        at /Users/hung-wulo/src/github.com/Shopify/vscode-ruby-lsp/out/test/suite/index.js:49:32
        at done (/Users/hung-wulo/src/github.com/Shopify/vscode-ruby-lsp/node_modules/mocha/lib/mocha.js:1012:7)
[main 2023-03-13T06:59:06.000Z] [UtilityProcess id: 1, type: extensionHost, pid: 55407]: waiting to exit...
[main 2023-03-13T06:59:06.011Z] [UtilityProcess id: 1, type: extensionHost, pid: 55407]: received exit event with code 0
[main 2023-03-13T06:59:06.011Z] Extension host with pid 55407 exited with code: 0, signal: unknown.
Exit code:   1
Failed to run tests
error Command failed with exit code 1.

Possibly related screenshot:

[vinistock]

I think it's because I used afterEach instead of after for restoring your configured version manager. Can you give it another try?

[st0012]

@vinistock Tests now all pass locally. Thanks 👍