metrics: use atomic type (#27121)

[thaarok]

Backport of metrics improvement removing a race condition.

Upstream commit:
ethereum/go-ethereum@ae93e0b

Race condition being fixed:

==================
WARNING: DATA RACE
Read at 0x00c005cf8c30 by goroutine 3549:
  github.com/ethereum/go-ethereum/metrics.(*StandardMeter).Snapshot()
      /home/jand/go/pkg/mod/github.com/!fantom-foundation/go-ethereum-substate@v1.1.1-0.20231003122306-febfe681b4a7/metrics/meter.go:244 +0x73
  github.com/ethereum/go-ethereum/metrics/exp.Exp.Handler.func1()
      /home/jand/go/pkg/mod/github.com/!fantom-foundation/go-ethereum-substate@v1.1.1-0.20231003122306-febfe681b4a7/metrics/prometheus/prometheus.go:55 +0x321
  net/http.HandlerFunc.ServeHTTP()
      /usr/local/go/src/net/http/server.go:2136 +0x47
  net/http.(*ServeMux).ServeHTTP()
      /usr/local/go/src/net/http/server.go:2514 +0xbc
  net/http.serverHandler.ServeHTTP()
      /usr/local/go/src/net/http/server.go:2938 +0x2a1
  net/http.(*conn).serve()
      /usr/local/go/src/net/http/server.go:2009 +0xc24
  net/http.(*Server).Serve.func3()
      /usr/local/go/src/net/http/server.go:3086 +0x4f

Previous write at 0x00c005cf8c30 by goroutine 2517:
  sync/atomic.AddInt64()
      /usr/local/go/src/runtime/race_amd64.s:289 +0xb
  sync/atomic.AddInt64()
      <autogenerated>:1 +0x15
  github.com/Fantom-foundation/go-opera/gossip.(*Service).processEvent()
      /home/jand/go-opera-norma/gossip/c_event_callbacks.go:261 +0x5dd
  github.com/Fantom-foundation/go-opera/gossip.newService.func2()
      /home/jand/go-opera-norma/gossip/service.go:259 +0xa4
  github.com/Fantom-foundation/go-opera/gossip.(*handler).makeDagProcessor.func3()
      /home/jand/go-opera-norma/gossip/handler.go:480 +0x16e
  github.com/Fantom-foundation/lachesis-base/gossip/dagordering.(*EventsBuffer).processCompleteEvent()
      /home/jand/go/pkg/mod/github.com/!fantom-foundation/lachesis-base@v0.0.0-20230629034932-42bae8eeb426/gossip/dagordering/event_buffer.go:145 +0x128
  github.com/Fantom-foundation/lachesis-base/gossip/dagordering.(*EventsBuffer).pushEvent()
      /home/jand/go/pkg/mod/github.com/!fantom-foundation/lachesis-base@v0.0.0-20230629034932-42bae8eeb426/gossip/dagordering/event_buffer.go:88 +0x152
  github.com/Fantom-foundation/lachesis-base/gossip/dagordering.(*EventsBuffer).PushEvent()
      /home/jand/go/pkg/mod/github.com/!fantom-foundation/lachesis-base@v0.0.0-20230629034932-42bae8eeb426/gossip/dagordering/event_buffer.go:66 +0x324
  github.com/Fantom-foundation/lachesis-base/gossip/dagprocessor.(*Processor).process()
      /home/jand/go/pkg/mod/github.com/!fantom-foundation/lachesis-base@v0.0.0-20230629034932-42bae8eeb426/gossip/dagprocessor/processor.go:181 +0x115
  github.com/Fantom-foundation/lachesis-base/gossip/dagprocessor.(*Processor).Enqueue.func2()
      /home/jand/go/pkg/mod/github.com/!fantom-foundation/lachesis-base@v0.0.0-20230629034932-42bae8eeb426/gossip/dagprocessor/processor.go:146 +0x5b4
  github.com/Fantom-foundation/lachesis-base/utils/workers.worker()
      /home/jand/go/pkg/mod/github.com/!fantom-foundation/lachesis-base@v0.0.0-20230629034932-42bae8eeb426/utils/workers/workers.go:66 +0xf2
  github.com/Fantom-foundation/lachesis-base/utils/workers.(*Workers).Start.func1()
      /home/jand/go/pkg/mod/github.com/!fantom-foundation/lachesis-base@v0.0.0-20230629034932-42bae8eeb426/utils/workers/workers.go:31 +0x90

Goroutine 3549 (running) created at:
  net/http.(*Server).Serve()
      /usr/local/go/src/net/http/server.go:3086 +0x80c
  net/http.(*Server).ListenAndServe()
      /usr/local/go/src/net/http/server.go:2985 +0xbc
  net/http.ListenAndServe()
      /usr/local/go/src/net/http/server.go:3239 +0x114
  github.com/Fantom-foundation/go-opera/debug.StartPProf.func1()
      /home/jand/go-opera-norma/debug/flags.go:262 +0x115

Goroutine 2517 (running) created at:
  github.com/Fantom-foundation/lachesis-base/utils/workers.(*Workers).Start()
      /home/jand/go/pkg/mod/github.com/!fantom-foundation/lachesis-base@v0.0.0-20230629034932-42bae8eeb426/utils/workers/workers.go:29 +0x32
  github.com/Fantom-foundation/lachesis-base/gossip/dagprocessor.(*Processor).Start()
      /home/jand/go/pkg/mod/github.com/!fantom-foundation/lachesis-base@v0.0.0-20230629034932-42bae8eeb426/gossip/dagprocessor/processor.go:80 +0x44
  github.com/Fantom-foundation/go-opera/gossip.(*handler).Start()
      /home/jand/go-opera-norma/gossip/handler.go:694 +0x9bc
  github.com/Fantom-foundation/go-opera/gossip.(*Service).Start()
      /home/jand/go-opera-norma/gossip/service.go:451 +0x504
==================