fix(status icon): Handle parallel completion requests

Description

The code suggestions loading state does not account for multiple in-flight completion requests. It can enter an invalid state (showing 'ready' when in fact it is 'loading'.

This applies to the language server, I have not checked the non-language server version to see if the issue exists there also.

More info: gitlab-org/editor-extensions/gitlab-lsp!125 (comment 1670891715)

Related Issues

Resolves #[issue_number]

How has this been tested?

1. Link the gitlab-lsp (tv/2023-11/cancellation-debounce-draft branch) and gitlab-vscode-extension (this branch) together.
2. Run the extension host.
3. Enable code suggestions and the language server in settings.json, restarting if necessary:

   {
     "gitlab.featureFlags.languageServer": true,
     "gitlab.aiAssistedCodeSuggestions.enabled": true
   }

4. Type into a text file, triggering some requests.
5. Observe the state of the gitlab icon in the status bar.

Recordings (if appropriate):

Note the code suggestions icon state at the bottom of the video:

before	after
debounce_recording	debounce_fixed

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation
• Chore (Related to CI or Packaging to platforms)
• Test gap