optimize: change err == xx to errors.Is(err, xx)

[mongobaba]

Replace all error comparisons (matching format: err == xx) with errors.Is(err, xx).

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 95.21%. Comparing base (2629636) to head (3cb0fbf).
Report is 21 commits behind head on master.

Additional details and impacted files

Files	Coverage Δ
core/iox/textlinescanner.go	100.00% <100.00%> (ø)
core/stores/redis/hook.go	100.00% <100.00%> (ø)
.../internal/clientinterceptors/tracinginterceptor.go	100.00% <100.00%> (ø)

... and 250 files with indirect coverage changes