Use typing forward references

[carmocca]

What does this PR do?

These can give circular imports.

Also removed one indentation level in LightningModule.log

Part of #7631

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[codecov]

Codecov Report

Merging #7770 (9b8ccdc) into master (a69beab) will decrease coverage by 0%.
The diff coverage is 96%.

@@          Coverage Diff           @@
##           master   #7770   +/-   ##
======================================
- Coverage      92%     92%   -0%     
======================================
  Files         199     199           
  Lines       12986   12985    -1     
======================================
- Hits        11994   11980   -14     
- Misses        992    1005   +13