Introduce commands to enable / disable Code Suggestions in GitLab

Belongs to epic &12106 (closed) which comprises of:

• #1115 (closed)
• #1116
• #1117

There exists a user setting in GitLab where code suggestions can be enabled / disabled, see:

• gitlab#425710 (closed)
• gitlab!132414 (merged)

In this issue, we want to introduce two VS Code commands that the user may execute to enable or disable the GitLab instance's enable/disable code suggestions user preference.

These commands will call the API of the GitLab instance configured.