When parallel apply and apply cache are enabled, the memory may exceed `tidb_mem_quota_apply_cache`

## Enhancement

https://github.com/pingcap/tidb/blob/095227d4ef77f15ef4e29f0e4b9782175c884f54/pkg/executor/internal/applycache/apply_cache.go#L86-L94

If there are concurrent puts, the append kv may exceed the memory limit.

Start in pkg/executor/internal/applycache/apply_cache.go at lines 86-94 and inspect how concurrent puts append key-values when parallel apply and the apply cache are enabled. Reproduce the concurrent case and verify that append memory remains within tidb_mem_quota_apply_cache.

Written by the indexing model from the issue text.