Memory leak on `PeerPessimisticLocks`

## Bug Report



`PeerPessimisticLocks` is a per-peer data structure that does not release its hash map's memory allocation when items are removed. This leads to a memory leak during bulk insert, delete, or update transactions issued sequentially to regions.

https://github.com/tikv/tikv/blob/3d2fddcc78618dec5aa1f4a29eba4ccf209e590e/components/raftstore/src/store/txn_ext.rs#L186-L192

A heap profile shows that the accumulated memory allocation from `PeerPessimisticLocks`s is around 8.56 GiB.

<img height="300" alt="Image" src="https://github.com/user-attachments/assets/bef305d2-5c03-4e09-85f5-82b40de92879" />

### What version of TiKV are you using?


v7.5.6

### What operating system and CPU are you using?


### Steps to reproduce


Issue bulk insert, delete, or update transactions sequentially to regions.

### What did you expect?

No memory leak.

### What did happened?

Memory leak.

	pub fn remove(&mut self, key: &Key) {
	if let Some((lock, _)) = self.map.remove(key) {
	let desc = key.len() + lock.memory_size();
	self.memory_size -= desc;
	GLOBAL_MEM_SIZE.sub(desc as i64);
	}
	}

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Memory leak on `PeerPessimisticLocks` #18799

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Memory leak on PeerPessimisticLocks #18799

Description

Bug Report

What version of TiKV are you using?

What operating system and CPU are you using?

Steps to reproduce

What did you expect?

What did happened?

Metadata

Metadata

Assignees

Labels

Type

Projects

Milestone

Relationships

Development

Issue actions

Memory leak on `PeerPessimisticLocks` #18799