Call on_load_checkpoint before loading state_dict

[rohitgr7]

What does this PR do?

Follow up #3996. This was missed in that PR.

Before submitting

• 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?
• 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

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 🙃

[awaelchli]

I think it makes sense, and it can be useful when the hook can change state dict before the weights are loaded.

[rohitgr7]

1. I am not familier with hpc_load/save. Should on_hpc_load be moved before load_state_dict too?
2. Also there isn't any datamodule.on_hpc_load, just like we have datamodule.on_load_checkpoint

[codecov]

Codecov Report

Merging #4057 into master will decrease coverage by 2%.
The diff coverage is 100%.

@@           Coverage Diff            @@
##           master   #4057     +/-   ##
========================================
- Coverage      92%     90%     -2%     
========================================
  Files         105     111      +6     
  Lines        7815    9900   +2085     
========================================
+ Hits         7194    8955   +1761     
- Misses        621     945    +324     

[Borda]

lgtm