patch 8.2.1444: error messages are spread out and names can be confusing

Problem:    Error messages are spread out and names can be confusing.
Solution:   Start moving error messages to a separate file and use clear
            names.
diff --git a/src/dict.c b/src/dict.c
index a5569e6..b351730 100644
--- a/src/dict.c
+++ b/src/dict.c
@@ -847,7 +847,7 @@
 	    if (evaluate)
 	    {
 		if (*skipwhite(*arg) == ':')
-		    semsg(_(e_no_white_before), ":");
+		    semsg(_(e_no_white_space_allowed_before), ":");
 		else
 		    semsg(_(e_missing_dict_colon), *arg);
 	    }
@@ -866,7 +866,7 @@
 	}
 	if (vim9script && (*arg)[1] != NUL && !VIM_ISWHITE((*arg)[1]))
 	{
-	    semsg(_(e_white_after), ":");
+	    semsg(_(e_white_space_required_after), ":");
 	    clear_tv(&tvkey);
 	    goto failret;
 	}
@@ -909,7 +909,7 @@
 	{
 	    if (vim9script && (*arg)[1] != NUL && !VIM_ISWHITE((*arg)[1]))
 	    {
-		semsg(_(e_white_after), ",");
+		semsg(_(e_white_space_required_after), ",");
 		goto failret;
 	    }
 	    *arg = skipwhite(*arg + 1);
@@ -924,7 +924,7 @@
 	    if (evaluate)
 	    {
 		if (**arg == ',')
-		    semsg(_(e_no_white_before), ",");
+		    semsg(_(e_no_white_space_allowed_before), ",");
 		else
 		    semsg(_(e_missing_dict_comma), *arg);
 	    }