Remove manual tracking of optimizer steps by the LightningOptimizer

[carmocca]

What does this PR do?

Related to #9661

Does your PR introduce any breaking changes? If yes, please list them.

None

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[codecov]

Codecov Report

Merging #9957 (293a965) into master (788f686) will decrease coverage by 0%.
The diff coverage is n/a.

@@          Coverage Diff           @@
##           master   #9957   +/-   ##
======================================
- Coverage      93%     93%   -0%     
======================================
  Files         179     179           
  Lines       15833   15831    -2     
======================================
- Hits        14673   14660   -13     
- Misses       1160    1171   +11     

[tchaton]

LGTM !