Add invariance check & logs to occ scheduler

[codchen]

Describe your changes and provide context

Add logs where certain implicit invariants in OCC scheduler are broken

Testing performed to validate your change

[codecov]

Codecov Report

Attention: Patch coverage is 80.00000% with 7 lines in your changes missing coverage. Please review.

Project coverage is 54.91%. Comparing base (4e7d467) to head (0ec7b87).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
tasks/scheduler.go	75.86%	5 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #545      +/-   ##
==========================================
+ Coverage   54.90%   54.91%   +0.01%     
==========================================
  Files         631      631              
  Lines       54920    54946      +26     
==========================================
+ Hits        30152    30174      +22     
- Misses      22614    22617       +3     
- Partials     2154     2155       +1     

Files with missing lines	Coverage Δ
store/multiversion/store.go	91.11% <100.00%> (+0.14%)	⬆️
tasks/scheduler.go	90.29% <75.86%> (-0.54%)	⬇️

... and 1 file with indirect coverage changes