release-8.5 lost WARN downgrades from #63494 in coprocessor & distsql

## Bug Report

On `release-8.5` the cherry-pick order `57522 → 63494` (release PRs #62100 and #63624) overwrote two WARN downgrades introduced by #63494:

1. `pkg/store/copr/coprocessor.go:1157-1164` (`liteCopIteratorWorker.liteSendReq`) still logs `logutil.Logger(ctx).Error("copIteratorWork meet
panic", …)` because #62100 (release cherry-pick of #57522) rewrote the block after #63624 (#63494) landed.
2. `pkg/executor/distsql.go:1234-1236` (`execTableTask`) also logs `"TableWorker in IndexLookUpExecutor panicked"` at ERROR. Master downgraded
this in #63494, but `release-8.5` keeps the old level because #62104 (release cherry-pick of #58033) came after #63624.

The corresponding master commits already use WARN (`pkg/store/copr/coprocessor.go:1199`, `pkg/executor/distsql.go:1486`). To keep release behavior
aligned, please reapply the WARN downgrade on `release-8.5`.

## Affected branch
`release-8.5` (after tags 8.5.3 → 8.5.4)

## Suggested fix
Cherry-pick the relevant hunks from #63494 or manually change the two log statements back to `logutil.Logger(...).Warn(...)` on `release-8.5`.