Introduce GitHub Merge Queue to `modulectl`

[amritanshusikdar]

Description:

From the brainstorming session of this issue, it was concluded that we first introduce GitHub Merge Queue to modulectl, before we do so on Lifecycle Manager.

Reasons:
Whenever there are multiple PRs awaiting a merge, any changes to the target branch (main in our case) or merging of another PR first, renders all the others outdated. Then they have to be manually rebased and the CI tests have to be run all over again. This is very cumbersome, especially when we have many small sized PRs like the ones from dependabot. The goal of introducing this change to the repository is to automate this process, in which the Merge Queues handle the rebasing and running of CI tests, as well as merging of the PRs when everything is green.

Resources:
A new trigger event with the name merge_group might come in handy. Please have a look here.

Acceptance Criteria:

• GitHub Merge Queue is supported for this repository.
• Batching feature is not enabled.
• The CI tests are triggered when the PRs are pushed onto the queue.
• Prepare a dummy PR to verify the feature