Add a lock to fix the panic while starting and loading the pool db.

[zjg555543]

It got a panic while pool had many tx and restart node agagin.
Error is concurrent map read and map write, at the code p.isLocalLRU.Add(string(v), struct{}{})

1. first goroutine

github.com/hashicorp/golang-lru/v2/simplelru.(*LRU[...]).Add() 
github.com/ledgerwatch/erigon/zk/txpool.(*TxPool).fromDB()
github.com/ledgerwatch/erigon/zk/txpool.(*TxPool).OnNewBlock()

2. second goroutine

github.com/ledgerwatch/erigon/zk/txpool.(*TxPool).fromDB()
github.com/ledgerwatch/erigon/zk/txpool.(*TxPool).StartIfNotStarted

So, use a lock here when loading the pool.

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

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