Transaction's memory usage is tracked multiple times

[ekexium]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

N/A

2. What did you expect to see? (Required)

Precise memory tracking.

3. What did you see instead (Required)

Transaction's memory usage is tracked by multiple times:

1. MemDB tracker
2. Stale tracking in executors like

   tidb/pkg/executor/replace.go

   Line 190 in 7b8c91d

   e.memTracker.Consume(int64(txn.Size() - txnSize))

4. What is your TiDB version? (Required)

master