Elasticsearch: HLRC: remove duplication from ascii docs

[pgomulka]

there is a way to decrease duplication when writing the documentation for HLRC

Things to fix:

• migration API - once commited #34898
• bulk API - mostly done by @nik9000 in #34925, small improvements in #35413
• reindex API - improvments in #35413

see #34925

[elasticmachine]

Pinging @elastic/es-core-infra

[nik9000]

I think it might be worth renaming this issue an using it to track those DRY-ing up tasks.

[pgomulka]

@jakelandis @nik9000 there is obviously always a way to improve the documentation, but I suppose that this issue can be now closed. It would be better to open a new one, then to have this one hanging around open.
what do you think?

[nik9000]

I thought we'd use this to track all of the DRY-ing up tasks. But I'm fine with whatever you'd prefer.

[jakelandis]

I still have a TODO reminder (that pops up weekly) to organize and distribute some of the work here. I have a minor preference to keep this one open since it has some relevant history. I suspect in the next couple weeks I will be able to update this (or a different) issue with something actionable.

[jrodewig]

[docs issue triage]

Leaving open. This is still relevant and planned for work.