Update PR Tagging For Release Failures

[scbedd]

• Additional Error Handling on Resolving an Identity
• Rework how users are added to a PR
• Allow Failed Tagging of a User on PR

My understanding after reading the github API docs was that the assignees setting was replaced by a push. It's actually additive, forgiving of duplicates. Adjust to push 1 at a time, turning the step yellow when any fail to add.

[praveenkuttappan]

Looks good.

[weshaggard]

@chidozieononiwu you can use this PR as a case study for what happens if the tools PR gets merged while the language Sync PR's are still open. You can see that newer sync PRs like https://github.com/Azure/azure-sdk-for-net/pull/14518/files have all the changes that are in tools master.

[chidozieononiwu]

@chidozieononiwu you can use this PR as a case study for what happens if the tools PR gets merged while the language Sync PR's are still open. You can see that newer sync PRs like https://github.com/Azure/azure-sdk-for-net/pull/14518/files have all the changes that are in tools master.

It doesn't seem that this would cause much grief. The bigger problem is when some Sync PRs are merged but the Tools PR is still opened. So new sync PRs end up replacing previously merged changes.

[weshaggard]

It ends up mixing multiple tools PRs together which might cause some issues, if nothing else it will cause pollution in the other PRs. At any rate we should get those other sync PR's merged.