Make move_metrics_to_cpu work recursively

[ddrevicky]

What does this PR do?

• Passes the to_cpu flag down the call chain in recursive_detach

Fixes #5831

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[codecov]

Codecov Report

Merging #6007 (a3fb718) into master (6d1e055) will decrease coverage by 3%.
The diff coverage is 70%.

@@           Coverage Diff           @@
##           master   #6007    +/-   ##
=======================================
- Coverage      93%     90%    -3%     
=======================================
  Files         159     159            
  Lines       11209   11080   -129     
=======================================
- Hits        10440   10007   -433     
- Misses        769    1073   +304     

[Borda]

@ddrevicky mind rebase/merge master regarding updated TPU configuration... 🐰

[tchaton]

LGTM ! Great catch !