Automatic merge from submit-queue (batch tested with PRs 54824, 55911, 55730, 55979, 55961). If you want to cherry-pick this change to another branch, please follow the instructions <a href="https://github.com/kubernetes/community/blob/master/contributors/devel/cherry-picks.md">here</a>.
Device plugin API merge of handler and manager
**What this PR does / why we need it**: We are trying different approaches to make the device plugin implementation simpler and more robust. One option is to merge the notion of the `device_plugin_handler` into the `device_manager`. This is for several reasons:
1) Some calls go directly from handler to manager, adding little value.
2) The separation of concern is not clear between the two components. They have a 1:1 relationship.
3) The separation and abstractions needed are at a different level. Code that can be refactored will most likely live in abstractions which hide details around lock acquisition and check pointing.
In this PR, we will **just** merge the two interfaces. After this, there is several opportunities for simplifying and cleaning up the device plugin.
Fixes#55180
**Special notes for your reviewer**: This is a WIP. May very well get dropped, but keeping up for the sake of early sharing and showing the progress of the code move.
**Release note**:
```release-note
NONE
```
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