Feature enhancement: make some long running operations can be tracked by _tasks API

[gaobinlong]

This is the code implementation task for opensearch-project/OpenSearch#6228. We should add some enhancement for the following long running operations to make them can be tracked by _tasks API :

• shrink
• split
• clone
• open
• forcemerge

We can implement this by adding a new query parameter wait_for_completion to the APIs, when the parameter is set to false, then the API will return a task immediately and run asynchronously, when the operation completes its result will be written to .tasks index.

[gaobinlong]

The PR has been submitted yet, now wait the core team to review the code.

[gaobinlong]

The PR is in reviewing process, one member of the core team has approved the PR, now wait another member to review the PR.

[gaobinlong]

The PR has been merged yet, close this issue as it's done.