Add functions to get MR comments from gitlab

[omrisarig13]

Add an action that will get all the MR comments from gitlab and open them in Vim.

These comments should be opened in the quickfixlist (or some close list) and the user should be able to jump between the locations of the various comments in the code.

This should be asynchronous (it goes to gitlab and fetch content, we shouldn't make the user wait for this time).

The user should be able to get different types of comments using different commands (for example, a command for unresolved comments, a command for discussion threads and so on...)