[CELEBORN-1629] Support to apply ratis election operation with RESTful api

[turboFei]

What changes were proposed in this pull request?

As title.

Why are the changes needed?

It is more friendly for customer experience and necessary for automation integration.

Does this PR introduce any user-facing change?

Introduce new RESTful apis.

How was this patch tested?

election transfer:

election pause and resume:

election step down:

[mridulm]

+CC @akpatnam25 FYI for CLI

[turboFei]

It is done for ratis election apis.

cc @mridulm

[turboFei]

cc @AngersZhuuuu I saw that you add the docs for ratis-shell.

also cc @waitinfuture @RexXiong

[turboFei]

Could you also add the usage of the Ratis REST API in https://celeborn.apache.org/docs/latest/celeborn_ratis_shell

Sure, will add it later

[RexXiong]

Thanks. merge to main(v0.6.0)