tests: replace significant invisible spaces with macros

To make them explicit, visible, avoid being accidentally trimmed.
Also prevents Git warnings, e.g. on `git am`.

Also:
- runtests: add support for `%spc%` and `%tab%` macros.
- test59: delete non-significant line-ending space.
- spacecheck.pl: drop line-ending whitespace exception for tests.

Closes #19300

.github/scripts/spacecheck.pl

@@ -42,10 +42,6 @@ my @need_crlf = (
     "\\.(bat|sln)\$",
 );
 
-my @space_at_eol = (
-    "^tests/data/test",
-);
-
 my @non_ascii_allowed = (
     '\xC3\xB6',  # UTF-8 for https://codepoints.net/U+00F6 LATIN SMALL LETTER O WITH DIAERESIS
 );
@@ -129,8 +125,7 @@ while(my $filename = <$git_ls_files>) {
         push @err, "content: must use LF EOL for this file type";
     }
 
-    if(!fn_match($filename, @space_at_eol) &&
-       $content =~ /[ \t]\n/) {
+    if($content =~ /[ \t]\n/) {
         my $line;
         for my $l (split(/\n/, $content)) {
             $line++;