Add support for using custom Environments and Strategies ⚡

[amorehead]

What does this PR do?

Adds the ability for one to employ custom (e.g., Lightning Fabric) Environments (e.g., SlurmEnvironment) and Strategies (e.g., DeepSpeedStrategy) during model training or evaluation.

Before submitting

• Did you make sure title is self-explanatory and the description concisely explains the PR?
• Did you make sure your PR does only one thing, instead of bundling different changes together?
• Did you list all the breaking changes introduced by this pull request?
• Did you test your PR locally with pytest command?
• Did you run pre-commit hooks with pre-commit run -a command?

Did you have fun?

Make sure you had fun coding 🙃 ⚡

[codecov-commenter]

Codecov Report

Attention: 29 lines in your changes are missing coverage. Please review.

Comparison is base (bddbc24) 83.24% compared to head (27fd562) 78.60%.

Files	Patch %	Lines
src/__init__.py	37.50%	10 Missing ⚠️
src/train.py	60.86%	9 Missing ⚠️
src/eval.py	50.00%	8 Missing ⚠️
src/models/mnist_module.py	50.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #608      +/-   ##
==========================================
- Coverage   83.24%   78.60%   -4.65%     
==========================================
  Files          11       12       +1     
  Lines         376      430      +54     
==========================================
+ Hits          313      338      +25     
- Misses         63       92      +29     

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