[tests] model-level `device_map` clarifications (#11681)
* add clarity in documentation for device_map
* docs
* fix how compiler tester mixins are used.
* propagate
* more
* typo.
* fix tests
* fix order of decroators.
* clarify more.
* more test cases.
* fix doc
* fix device_map docstring in pipeline_utils.
* more examples
* more
* update
* remove code for stuff that is already supported.
* fix stuff.
