Add static analyzer to discourage use of panic() (#15075)

* Implement static analysis to prevent panics

* Add nopanic to nogo

* Fix violations and add exclusions

Fix violations and add exclusions for all

* Changelog fragment

* Use pass.Report instead of pass.Reportf

* Remove strings.ToLower for checking init method name

* Add exclusion for herumi init

* Move api/client/beacon template function to init and its own file

* Fix nopanic testcase

cmd/wrap_flags.go

@@ -34,11 +34,11 @@ func WrapFlags(flags []cli.Flag) []cli.Flag {
 			f = altsrc.NewPathFlag(t)
 		case *cli.Int64Flag:
 			// Int64Flag does not work. See https://github.com/prysmaticlabs/prysm/issues/6478
-			panic(fmt.Sprintf("unsupported flag type %T", f))
+			panic(fmt.Sprintf("unsupported flag type %T", f)) // lint:nopanic -- This is evaluated at application start.
 		case *cli.IntSliceFlag:
 			f = altsrc.NewIntSliceFlag(t)
 		default:
-			panic(fmt.Sprintf("cannot convert type %T", f))
+			panic(fmt.Sprintf("cannot convert type %T", f)) // lint:nopanic -- This is evaluated at application start.
 		}
 		wrapped = append(wrapped, f)
 	}