Monitor service (#9933)

* Add a service for the monitor

* Do not block service start

* gaz

* move channel subscription outide go routine

* add service start test

* fix panic on node tests

* Radek's first pass

* Radek's take 2

* uncap error messages

* revert reversal

* Terence take 1

* gaz

* Missing locks found by Terence

* Track via bool not empty interface

* Add tests for every function

* fix allocation of slice

* Minor cleanups

Co-authored-by: terence tsao <terence@prysmaticlabs.com>

cmd/wrap_flags.go

@@ -33,6 +33,8 @@ func WrapFlags(flags []cli.Flag) []cli.Flag {
 		case *cli.Int64Flag:
 			// Int64Flag does not work. See https://github.com/prysmaticlabs/prysm/issues/6478
 			panic(fmt.Sprintf("unsupported flag type type %T", f))
+		case *cli.IntSliceFlag:
+			f = altsrc.NewIntSliceFlag(t)
 		default:
 			panic(fmt.Sprintf("cannot convert type %T", f))
 		}