Raptor background jobs

[kewang1024]

== Raptor ==
- Add delta delete support in Raptor. If table property "table_supports_delta_delete" is set to true
when creating a Raptor table, DELETE query will write down "tombstones" of deleted data instead 
of rewriting files immediately. 

[kewang1024]

Given the last PR is still in process, this PR still have some commits from last PR.
But we can first review the logic and coding style in
Enable delta compaction and organization
Add priority to Compaction process
Add delta in reassign process

I will create a new PR after the last PR is merged.
@jessesleeping @highker

Thanks!

[highker]

some comments

[jessesleeping]

Reviewed commit "Enable delta compaction and organization". Only minor comments.

[jessesleeping]

Reviewed commit "Add priority to Compaction process". Some general comments besides the inline minor comments:

• Instead of using int to indicate priority, I suggest we use an enum which has DELTA_COMPACTION and NORMAL_COMPACTION for now. It will be more readable.
• Can you add test case to verify if the behavior of ShardOrganizer is as expected?

[jessesleeping]

Instead of adding 2 levels of callback, can you extract the for loop into a function and call it at onSuccess() and onFailure() below?

[kewang1024]

But that would add duplicate code, Let's also confirm with James before we make this change

[jessesleeping]

Why would this create duplicate code?

[jessesleeping]

Commit "Add delta in reassign process" LGTM.

[kewang1024]

• DELTA_COMPACTION

But currently I also add how many delta we have as the priority, so that the OrganizationSet that has the most delta will be compacted first, so the number couldn't be abstracted as ENUM for now

[highker]

Could you rebase?

[kewang1024]

the third PR of #13248

[highker]

nits only. Will leave to @jessesleeping for the final approval and merge.