[TypeSpec to SDK flow] improve the review process

Currently, we need to ask service team to merge the pr after we have approved, but sometimes, service team are not respond to the pr merge in time, which could cause the pr has conflicts. And ci require approval for last commit and we have to spend time to approve the pr for multiple times and it's very inconvenient. See this pr as an example https://github.com/Azure/azure-sdk-for-js/pull/34273.

I wonder if we can change the review process as https://github.com/Azure/azure-sdk-for-js/pull/34667 this PR shows.
1. We prepare the PR and close the issue.
2. Service team review the PR, if they agrees with the change, they can approve and enable auto-merge.
3. We will review the PR after step 2. Once we approve, it should meet all merge requirements, and auto-merge should be able to merge this pr.

In this way, we only need to approve once and the overall communication effort is less.