Fix load disparity between normal and hpc

[tarepan]

What does this PR do?

Fix disparity/feature-lack in hpc load compared to normal load (#1947, #4381).

Current hpc_load do not have datamodule restore & on_load_checkpoint, which are implemented in normal load (restore).
This PR converge this gap with common restore_model_states function.

Before submitting

• pointed out <= Was this discussed/approved via a Github issue? (no need for typos and docs improvements)
• 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? Otherwise, we ask you to create a separate PR for every change.
• Did you make sure to update the documentation with your changes?
• [n/a] Did you write any new necessary tests?
• Did you verify new and existing tests pass locally with your changes?
• If you made a notable change (that affects users), did you update the CHANGELOG?

PR review

• Is this pull request ready for review? (if not, please submit in draft mode)

Anyone in the community is free to review the PR once the tests have passed.
If we didn't discuss your PR in Github issues there's a high chance it will not be merged.

Did you have fun?

Make sure you had fun coding 👍

[codecov]

Codecov Report

Merging #4526 (04771fa) into master (23719e3) will decrease coverage by 0%.
The diff coverage is 82%.

@@          Coverage Diff           @@
##           master   #4526   +/-   ##
======================================
- Coverage      93%     93%   -0%     
======================================
  Files         116     116           
  Lines        8833    8831    -2     
======================================
- Hits         8235    8232    -3     
- Misses        598     599    +1     

[tchaton]

Looks great !

[SeanNaren]

Weirdness with the TPU test, will keep an eye on it to ensure it passes.