{CI} Auto merge release pull reqeust create by azclibot

[wangzelin007]

---

We need to merge the PR created by azclibot in time.
Otherwise the index.json from the new PR does not contain the contents of the old PR.
And we must create a PR to fix the index.json conflict problem.
Such as: #4940 #4779

This PR will auto merge the PR created by azclibot.
For old steps, we still modify in Azure CLI Extensions Release pipeline.

For new steps, we add scripts in scripts/release directory. (For easy tracking and reviewing.)

There is a new pipeline Azure CLI Extensions Release Test Auto Merge to test auto merge.

This checklist is used to make sure that common guidelines for a pull request are followed.

Related command

General Guidelines

• Have you run azdev style <YOUR_EXT> locally? (pip install azdev required)
• Have you run python scripts/ci/test_index.py -q locally?

For new extensions:

• My extension description/summary conforms to the Extension Summary Guidelines.

About Extension Publish

There is a pipeline to automatically build, upload and publish extension wheels.
Once your pull request is merged into main branch, a new pull request will be created to update src/index.json automatically.
The precondition is to put your code inside this repository and upgrade the version in the pull request but do not modify src/index.json.

[yonzhan]

CI

[kairu-ms]

Why not fetch token from keyvault?

[wangzelin007]

In old steps, we can use environment variable Azure subscription in Azure CLI option.
So it is easy to use azure cli command.
And the token.txt is get from the az keyvault commmand in last step, and the transfer between the two steps can only use a temporary file.
We have used another temporary file upgrade_extensions.txt to identify if there are extensions that need to be upgraded.

But new step I use python script which not support environment variable.
And after the job finished (about 4 mins) this agent will be delete, so I think it is safe.

[jiasli]

Can't we use Arguments?