feat: logging sql read amplification

[kevwan]

1. logging concurrent same queries to let developers know where to prevent read amplification
2. the solution is to use syncx.SingleFlight to prevent concurrent reading of the same results

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 95.18%. Comparing base (8690859) to head (8c3843a).
Report is 10 commits behind head on master.

Additional details and impacted files

Files	Coverage Δ
core/stores/sqlx/readamplication.go	100.00% <100.00%> (ø)
core/stores/sqlx/stmt.go	100.00% <100.00%> (ø)

... and 254 files with indirect coverage changes