test(hc): Run unit tests in region silo mode by default

[RyanSkonnord]

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 84.25%. Comparing base (0daa386) to head (1cd6bdb). Report is 11 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master   #62210   +/-   ##
=======================================
  Coverage   84.24%   84.25%           
=======================================
  Files        5295     5295           
  Lines      236624   236625    +1     
  Branches    40967    40967           
=======================================
+ Hits       199345   199357   +12     
+ Misses      37060    37049   -11     
  Partials      219      219           

Files	Coverage Δ
src/sentry/testutils/pytest/sentry.py	86.66% <100.00%> (-0.07%)	:arrow_down:

... and 8 files with indirect coverage changes