Ci/CD Automatic conflict resolving does not work

[VitalyGushin]

#1111
#1112

[NikitaSkrynnik]

Another Issue

When we have conflicts in PRs ci workflow doesn't start. We should check and resolve any conflicts on PR creation. Steps:

1. Copy check-mergeability and resolve-conflicts jobs and put them after this job
2. Remove this condition from the copied check-mergeability job
3. Add needs: [auto-pull-request] into conditions of the copied check-mergeability job

[Ex4amp1e]

Action plan

1. Finish Added comment with draft field info to reuse .github#78
2. Test Check and resolve conflicts on PR creation #1118
3. Provide fix from [2] to https://github.com/networkservicemesh/cmd-template

[denis-tingaikin]

Latest incidents: #1209, #1211

[LionelJouin]

I checked the CI: https://github.com/networkservicemesh/.github/blob/main/.github/workflows/check-mergeability.yaml
The caller of this job is ran on push event: https://github.com/networkservicemesh/cmd-forwarder-vpp/blob/main/.github/workflows/pr-for-updates.yaml

This means that github.event.workflow_run.head_branch will be null.

A way to avoid that would be to check if github.event.workflow_run is null and use something like github.event.push.head_commit instead (https://docs.github.com/en/webhooks/webhook-events-and-payloads#push)

[denis-tingaikin]

PR is welcome ;)