Deprecate add_to_queue and get_from_queue from Lightning Module

[daniellepintz]

What does this PR do?

Fixes #8940

Deprecates add_to_queue/get_from_queue from Lightning Module. To address #7671 in v1.7 we will put trainer.callback_metrics directly on the queue in __transfer_distrib_spawn_state_on_fit_end and get it from the queue in post_dispatch.

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[ananthsub]

what's the relation between this and #9118 ?

[daniellepintz]

@ananthsub #9118 was a first attempt, I have closed it and I am not planning to merge it, in favor of this PR.

[codecov]

Codecov Report

Merging #9126 (a5abfe9) into master (045c879) will increase coverage by 0%.
The diff coverage is 100%.

@@          Coverage Diff           @@
##           master   #9126   +/-   ##
======================================
  Coverage      88%     88%           
======================================
  Files         176     176           
  Lines       14808   14814    +6     
======================================
+ Hits        13036   13042    +6     
  Misses       1772    1772           

[daniellepintz]

Closing in favor of #9118