Add Goland Standard "cmd" Pattern for Beacon-Chain Binaries (#8540)

* beacon chain cmd pattern

* imports spacing

* more import fix

* edit build file

* e2e viz

* amend e2e

cmd/beacon-chain/usage_test.go

@@ -0,0 +1,44 @@
+package main
+
+import (
+	"testing"
+
+	"github.com/prysmaticlabs/prysm/shared/featureconfig"
+	"github.com/urfave/cli/v2"
+)
+
+func TestAllFlagsExistInHelp(t *testing.T) {
+	// If this test is failing, it is because you've recently added/removed a
+	// flag in beacon chain main.go, but did not add/remove it to the usage.go
+	// flag grouping (appHelpFlagGroups).
+
+	var helpFlags []cli.Flag
+	for _, group := range appHelpFlagGroups {
+		helpFlags = append(helpFlags, group.Flags...)
+	}
+	helpFlags = featureconfig.ActiveFlags(helpFlags)
+	appFlags = featureconfig.ActiveFlags(appFlags)
+
+	for _, flag := range appFlags {
+		if !doesFlagExist(flag, helpFlags) {
+			t.Errorf("Flag %s does not exist in help/usage flags.", flag.Names()[0])
+		}
+	}
+
+	for _, flag := range helpFlags {
+		if !doesFlagExist(flag, appFlags) {
+			t.Errorf("Flag %s does not exist in main.go, "+
+				"but exists in help flags", flag.Names()[0])
+		}
+	}
+}
+
+func doesFlagExist(flag cli.Flag, flags []cli.Flag) bool {
+	for _, f := range flags {
+		if f.String() == flag.String() {
+			return true
+		}
+	}
+
+	return false
+}