fix race condition when pinging peers

[qu0b]

What type of PR is this?

Bug fix found using Antithesis

What does this PR do? Why is it needed?

Fixes a race condition where the underlying pingMethod changes while it is being read and vice versa.

WARNING: DATA RACE
Read at #HEX by go routine: #DIG:
  github.com/prysmaticlabs/prysm/v5/beacon-chain/p2p.(*Service).pingPeers()
      beacon-chain/p2p/service.go:361 +0x37
  github.com/prysmaticlabs/prysm/v5/beacon-chain/p2p.(*Service).RefreshENR()
      beacon-chain/p2p/discovery.go:94 +0xa7a
  github.com/prysmaticlabs/prysm/v5/beacon-chain/p2p.(*Service).Start()
      beacon-chain/p2p/service.go:218 +0xe24
  github.com/prysmaticlabs/prysm/v5/runtime.(*ServiceRegistry).StartAll.func1()
      runtime/service_registry.go:46 +0x42
Previous write at #HEX by go routine: #DIG:
  github.com/prysmaticlabs/prysm/v5/beacon-chain/p2p.(*Service).AddPingMethod()
      beacon-chain/p2p/service.go:357 +0x37
  github.com/prysmaticlabs/prysm/v5/beacon-chain/sync.(*Service).Start()
      beacon-chain/sync/service.go:234 +0x67c
  github.com/prysmaticlabs/prysm/v5/runtime.(*ServiceRegistry).StartAll.func1()
      runtime/service_registry.go:46 +0x42
go routine: #DIG (running) created at:
  github.com/prysmaticlabs/prysm/v5/runtime.(*ServiceRegistry).StartAll()
      runtime/service_registry.go:46 +0x17e
  github.com/prysmaticlabs/prysm/v5/beacon-chain/node.(*BeaconNode).Start()
      beacon-chain/node/node.go:378 +0x1ed
  main.startNode()
      cmd/beacon-chain/main.go:311 +0xc26
  main.main.func1()
      cmd/beacon-chain/main.go:160 +0x38
  github.com/urfave/cli/v2.(*Command).Run()
      external/com_github_urfave_cli_v2/command.go:274 +0x13f4
  github.com/urfave/cli/v2.(*App).RunContext()
      external/com_github_urfave_cli_v2/app.go:332 +0x1249
  main.main()
      cmd/beacon-chain/main.go:233 +0x58a
go routine: #DIG (finished) created at:
  github.com/prysmaticlabs/prysm/v5/runtime.(*ServiceRegistry).StartAll()
      runtime/service_registry.go:46 +0x17e
  github.com/prysmaticlabs/prysm/v5/beacon-chain/node.(*BeaconNode).Start()
      beacon-chain/node/node.go:378 +0x1ed
  main.startNode()
      cmd/beacon-chain/main.go:311 +0xc26
  main.main.func1()
      cmd/beacon-chain/main.go:160 +0x38
  github.com/urfave/cli/v2.(*Command).Run()
      external/com_github_urfave_cli_v2/command.go:274 +0x13f4
  github.com/urfave/cli/v2.(*App).RunContext()
      external/com_github_urfave_cli_v2/app.go:332 +0x1249
  main.main()
      cmd/beacon-chain/main.go:233 +0x58a