Update debug-migration function changes to be backwards-compatible.

[aemous]

Description of changes:

• For all public function signatures modified in Merge --v2-debug migration debug mode to develop #9905, modified their signatures so that the new arguments are added to the end with defaults provided.
• For new callback handlers using the new remaining_args argument on the top-level-args-parsed event, update them to handle the case that remaining_args is None, for backwards compatibility.
• For the top-level-args event emission, move the new remaining_args argument to the end, to avoid breaking existing

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Description of tests:

• Successfully ran and passed all unit and functional tests.
• Successfully ran a test build.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.34%. Comparing base (5a98bdf) to head (da11c28).
⚠️ Report is 137 commits behind head on debug-migration.

Additional details and impacted files

@@                 Coverage Diff                 @@
##           debug-migration    #9916      +/-   ##
===================================================
+ Coverage            93.32%   93.34%   +0.02%     
===================================================
  Files                  209      209              
  Lines                16909    16938      +29     
===================================================
+ Hits                 15780    15811      +31     
+ Misses                1129     1127       -2     

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