patch 8.2.3069: error messages are spread out

Problem:    Error messages are spread out.
Solution:   Move some error messages to errors.h.  Use clearer names.
diff --git a/src/eval.c b/src/eval.c
index 7990c23..f570016 100644
--- a/src/eval.c
+++ b/src/eval.c
@@ -216,7 +216,7 @@
 	// Also check called_emsg for when using assert_fails().
 	if (!aborting() && did_emsg == did_emsg_before
 					  && called_emsg == called_emsg_before)
-	    semsg(_(e_invexpr2), start);
+	    semsg(_(e_invalid_expression_str), start);
     }
     clear_evalarg(&evalarg, eap);
     return ret;
@@ -297,7 +297,7 @@
 	if (*skipwhite(s) != NUL)  // check for trailing chars after expr
 	{
 	    clear_tv(rettv);
-	    semsg(_(e_invexpr2), s);
+	    semsg(_(e_invalid_expression_str), s);
 	    return FAIL;
 	}
     }
@@ -2268,7 +2268,7 @@
 	    if (end_error)
 		semsg(_(e_trailing_arg), p);
 	    else
-		semsg(_(e_invexpr2), arg);
+		semsg(_(e_invalid_expression_str), arg);
 	}
 
 	// Some of the expression may not have been consumed.  Do not check for
@@ -2758,7 +2758,7 @@
 
 	if (vim9script && type_is && (p[len] == '?' || p[len] == '#'))
 	{
-	    semsg(_(e_invexpr2), p);
+	    semsg(_(e_invalid_expression_str), p);
 	    clear_tv(rettv);
 	    return FAIL;
 	}
@@ -3367,7 +3367,7 @@
 	// ++, --, -+ and +- are not accepted in Vim9 script
 	if (vim9 && (*p == '-' || *p == '+') && (*n == '-' || *n == '+'))
 	{
-	    semsg(_(e_invexpr2), s);
+	    semsg(_(e_invalid_expression_str), s);
 	    return FAIL;
 	}
 	p = n;
@@ -3441,7 +3441,7 @@
 #endif
 	    ))
     {
-	semsg(_(e_invexpr2), *arg);
+	semsg(_(e_invalid_expression_str), *arg);
 	++*arg;
 	return FAIL;
     }
@@ -5607,7 +5607,7 @@
     // Only give an error when there is something, otherwise it will be
     // reported at a higher level.
     if (len == 0 && verbose && **arg != NUL)
-	semsg(_(e_invexpr2), *arg);
+	semsg(_(e_invalid_expression_str), *arg);
 
     return len;
 }
@@ -6153,7 +6153,7 @@
 	     */
 	    if (!aborting() && did_emsg == did_emsg_before
 					  && called_emsg == called_emsg_before)
-		semsg(_(e_invexpr2), arg_start);
+		semsg(_(e_invalid_expression_str), arg_start);
 	    need_clr_eos = FALSE;
 	    break;
 	}