zsh fixes (zmodload, k8s, new var type, track zsh prompt) (#473)

* checkpoint.  track zmodloads, get the expanded PS1 value, change how we store and deal with 'prompt vars', add commands to track k8s context

* fix some warnings, change IsPVar to IsExtVar, checkpoint

* parse zmodloads into state

* restore zmodloads, be more careful around readonly variable setting to avoid errors

wavesrv/pkg/cmdrunner/shparse.go

@@ -214,6 +214,7 @@ var literalRtnStateCommands = []string{
 	"enable",
 	"disable",
 	"function",
+	"zmodload",
 }
 
 func getCallExprLitArg(callExpr *syntax.CallExpr, argNum int) string {