Move from master to main (step2)

[reyang]

Follow up on #531.

Please run the following commands on your local clone to migrate over:

git branch -m master main
git fetch origin
git branch -u origin/main main

[codecov]

Codecov Report

Merging #533 (1fbfee8) into main (484700a) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main     #533   +/-   ##
=======================================
  Coverage   94.45%   94.45%           
=======================================
  Files         194      194           
  Lines        8509     8509           
=======================================
  Hits         8037     8037           
  Misses        472      472           

Impacted Files	Coverage Δ
sdk/test/common/circular_buffer_test.cc	98.97% <0.00%> (-1.03%)	⬇️
sdk/test/metrics/counter_aggregator_test.cc	100.00% <0.00%> (+1.78%)	⬆️