1/n Move precision plugin into strategy - update reference

[four4fish]

What does this PR do?

1/n Move Precision Plugin into Strategy and update references
2/n Move optimizer, lr to Strategy, remove accelerator routing functions
3/n Simplify and reduce hooks and redundancies

Fixes #7324 which is part of #10416

Does your PR introduce any breaking changes? If yes, please list them.

Before submitting

• Was this discussed/approved via a GitHub issue? (not for typos and docs)
• Did you read the contributor guideline, Pull Request section?
• Did you make sure your PR does only one thing, instead of bundling different changes together?
• Did you make sure to update the documentation with your changes? (if necessary)
• Did you write any new necessary tests? (not for typos and docs)
• Did you verify new and existing tests pass locally with your changes?
• Did you list all the breaking changes introduced by this pull request?
• Did you update the CHANGELOG? (not for typos, docs, test updates, or internal minor changes/refactorings)

PR review

Anyone in the community is welcome to review the PR.
Before you start reviewing make sure you have read Review guidelines. In short, see the following bullet-list:

• Is this pull request ready for review? (if not, please submit in draft mode)
• Check that all items from Before submitting are resolved
• Make sure the title is self-explanatory and the description concisely explains the PR
• Add labels and milestones (and optionally projects) to the PR so it can be classified

Did you have fun?

Make sure you had fun coding 🙃

[ananthsub]

It'd be very good to list what APIs this lets us simplify or remove from the Accelerator/strategy/precision plugin. Those could be listed as immediate followups to this PR

[four4fish]

@tchaton @carmocca Addressed the comments, could you guys take a look?

1. Now this 1/n is backward compatible.
2. Updated the deprecation message and format. Add to @awaelchli mentioned before: there will breaking change in refactor step3 "move accelerator into strategy". Which means we will have to remove precision_plugin param from Accelerator BEFORE we have a stable version to release. So the deprecation message is "will be deprecated soon" instead of "deprecated in 1.6 remove in 1.7"

[kaushikb11]

LGTM! Thanks @four4fish