runtime(vim): Update base-syntax file, improve class, enum and interface highlighting

- Enable folding of class, enum and interface declarations.
- Highlight constructor names with the Function highlight group, like
  other special methods.
- Mark function definitions using special method names as errors.
- Highlight :type arguments.

fixes: #14393#issuecomment-2042796198.
closes: #13810

Signed-off-by: Doug Kearns <dougkearns@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>

runtime/syntax/testdir/dumps/vim_ex_commands_66.dump

@@ -1,20 +1,20 @@
-| +0&#ffffff0@74
-@75
-|"+0#0000e05&| |V|i|m|9|-|s|c|r|i|p|t| |o|n|l|y| +0#0000000&@56
-@75
-|:|a+0#af5f00255&|b|s|t|r|a|c|t| +0#0000000&@65
->:|c+0#af5f00255&|l|a|s@1| +0#0000000&@68
-|:|d+0#af5f00255&|e|f|c|o|m|p|i|l|e| +0#0000000&@63
-|:|d+0#af5f00255&|i|s|a|s@1|e|m|b|l|e| +0#0000000&@62
-|:|e+0#af5f00255&|n|d|c|l|a|s@1| +0#0000000&@65
-|:|e+0#af5f00255&|n|d|i|n|t|e|r|f|a|c|e| +0#0000000&@61
-|:|e+0#af5f00255&|n|d|e|n|u|m| +0#0000000&@66
-|:|e+0#af5f00255&|n|u|m| +0#0000000&@69
-|:|e+0#af5f00255&|x|p|o|r|t| +0#0000000&@67
+|:+0&#ffffff0|a+0#af5f00255&|b|s|t|r|a|c|t| +0#0000000&@65
+|:|c|l|a|s@1| @68
+|:|e|n|d|c|l|a|s@1| @65
+|:|e|n|d|i|n|t|e|r|f|a|c|e| @61
+|:|e|n|d|e|n|u|m| @66
+>:|e|n|u|m| @69
+|:|e|x|p|o|r|t| @67
 |:|f+0#af5f00255&|i|n|a|l| +0#0000000&@68
-|:|i+0#af5f00255&|n|t|e|r|f|a|c|e| +0#0000000&@64
-|:|p+0#af5f00255&|u|b|l|i|c| +0#0000000&@67
-|:|s+0#af5f00255&|t|a|t|i|c| +0#0000000&@67
-|:|t+0#af5f00255&|y|p|e| +0#0000000&@69
+|:|i|n|t|e|r|f|a|c|e| @64
+|:|p|u|b|l|i|c| @67
+|:|s|t|a|t|i|c| @67
+|:|t|y|p|e| @69
 |:|v+0#af5f00255&|a|r| +0#0000000&@70
-@57|1@1|8|9|,|1| @7|9|8|%| 
+@75
+|F|o@1|(+0#e000e06&|)| +0#0000000&||| |a+0#af5f00255&|b|s|t|r|a|c|t| +0#0000000&@58
+|F|o@1|(+0#e000e06&|)| +0#0000000&||| |c|l|a|s@1| @61
+|F|o@1|(+0#e000e06&|)| +0#0000000&||| |e|n|d|c|l|a|s@1| @58
+|F|o@1|(+0#e000e06&|)| +0#0000000&||| |e|n|d|e|n|u|m| @59
+|F|o@1|(+0#e000e06&|)| +0#0000000&||| |e|n|d|i|n|t|e|r|f|a|c|e| @54
+@57|1@1|8|9|,|1| @7|9@1|%|