runtime(vim): Update base-syntax, improve script-interface command highlighting

- Normalise interface heredoc highlighting with that used for
  :let-heredocs.
- Remove interface feature testing.  The Lua and Python interface
  command scripts are now highlighted by default.  Loading all syntax
  files incurs an undesirable load-time burden so highlighting of the
  less popular MzScheme, Perl, Ruby and Tcl interfaces is disabled by
  default.  g:vimsyn_embed can still be used to customise the supported
  interfaces.
- Always highlight interface ex-commands as valid commands, even when
  the corresponding command-script highlighting is disabled.
- Highlight simple command-script statements as well as heredocs.
- Remove error highlighting of heredoc and statement command-script
  regions when an interface is disabled.  These are now highlighted as
  plain text.
- Allow indented heredoc end tokens when "trim" is specified.
- Match interface heredocs in :def functions.
- Fix runaway vimEmbedError regions.  These regions have been removed.
- Use python2 syntax for :python, and :pythonx when 'pyxversion' is
  appropriately set.

closes: vim#15522

Signed-off-by: Doug Kearns <[email protected]>
Signed-off-by: Christian Brabandt <[email protected]>

Author: dkearns

runtime/doc/syntax.txt

@@ -1,4 +1,4 @@
-*syntax.txt*	For Vim version 9.1.  Last change: 2025 May 10
+*syntax.txt*	For Vim version 9.1.  Last change: 2025 May 17
 
 
 		  VIM REFERENCE MANUAL	  by Bram Moolenaar
@@ -3996,6 +3996,7 @@ names whose syntax definitions will be included in Typst files. Example: >
 
 VIM			*vim.vim*		*ft-vim-syntax*
 			*g:vimsyn_minlines*	*g:vimsyn_maxlines*
+
 There is a trade-off between more accurate syntax highlighting versus screen
 updating speed.  To improve accuracy, you may wish to increase the
 g:vimsyn_minlines variable.  The g:vimsyn_maxlines variable may be used to
@@ -4019,10 +4020,9 @@ embedded script highlighting they wish to have. >
    g:vimsyn_embed =~ 'r' : support embedded Ruby
    g:vimsyn_embed =~ 't' : support embedded Tcl
 <
-By default, g:vimsyn_embed is a string supporting interpreters that your vim
-itself supports.  Concatenate the indicated characters to support multiple
-types of embedded interpreters (e.g., g:vimsyn_embed = "mp" supports embedded
-mzscheme and embedded perl).
+By default, g:vimsyn_embed is unset, and the Lua and Python script interfaces
+are supported.
+
 						*g:vimsyn_folding*
 Some folding is now supported with when 'foldmethod' is set to "syntax": >
 
@@ -4031,15 +4031,15 @@ Some folding is now supported with when 'foldmethod' is set to "syntax": >
    g:vimsyn_folding =~ 'c' : fold Vim9 classes
    g:vimsyn_folding =~ 'e' : fold Vim9 enums
    g:vimsyn_folding =~ 'f' : fold functions
-   g:vimsyn_folding =~ 'h' : fold heredocs
+   g:vimsyn_folding =~ 'h' : fold let heredocs
    g:vimsyn_folding =~ 'i' : fold Vim9 interfaces
    g:vimsyn_folding =~ 'H' : fold Vim9 legacy headers
-   g:vimsyn_folding =~ 'l' : fold Lua      script
-   g:vimsyn_folding =~ 'm' : fold MzScheme script
-   g:vimsyn_folding =~ 'p' : fold Perl     script
-   g:vimsyn_folding =~ 'P' : fold Python   script
-   g:vimsyn_folding =~ 'r' : fold Ruby     script
-   g:vimsyn_folding =~ 't' : fold Tcl      script
+   g:vimsyn_folding =~ 'l' : fold Lua      heredocs
+   g:vimsyn_folding =~ 'm' : fold MzScheme heredocs
+   g:vimsyn_folding =~ 'p' : fold Perl     heredocs
+   g:vimsyn_folding =~ 'P' : fold Python   heredocs
+   g:vimsyn_folding =~ 'r' : fold Ruby     heredocs
+   g:vimsyn_folding =~ 't' : fold Tcl      heredocs
 <
 
 By default, g:vimsyn_folding is unset.  Concatenate the indicated characters

runtime/syntax/generator/gen_syntax_vim.vim

@@ -1,7 +1,7 @@
 " Vim syntax file generator
-" Language: Vim script
-" Maintainer: Hirohito Higashi (h_east)
-" Last Change: 2025 Apr 27
+" Language:		 Vim script
+" Maintainer:  Hirohito Higashi (h_east)
+" Last Change: 2025 May 16
 
 let s:keepcpo= &cpo
 set cpo&vim
@@ -301,14 +301,32 @@ function s:get_vim_command_type(cmd_name)
 		lvimgrep
 		lvimgrepadd
 		make
+		lua
+		luado
+		luafile
 		map
 		mapclear
 		match
+		mzscheme
+		mzfile
 		noremap
 		new
 		normal
+		perl
+		perldo
 		popup
 		public
+		python
+		pyfile
+		pydo
+		python3
+		py3
+		py3do
+		py3file
+		pythonx
+		pyx
+		pyxdo
+		pyxfile
 		redir
 		return
 		set
@@ -321,6 +339,9 @@ function s:get_vim_command_type(cmd_name)
 		static
 		substitute
 		syntax
+		tcl
+		tcldo
+		tclfile
 		this
 		throw
 		type