vim-patch:8.2.{1536,1540}: charclass() (#19748)

vim-patch:8.2.1536: cannot get the class of a character; emoji widths are wrong

Problem:    Cannot get the class of a character; emoji widths are wrong in
            some environments.
Solution:   Add charclass(). Update some emoji widths.  Add script to check
            emoji widths.
4e4473c927

Use latest charclass() docs from Vim.
Rewrite DoIt() in emoji_list.vim in Lua.
Omit emoji table updates:
- emoji_width update looks wrong as these added ranges are only double-width when followed by 0xFE0F.
- Other updates are too old.

vim-patch:8.2.1540: the user cannot try out emoji character widths

Problem:    The user cannot try out emoji character widths.
Solution:   Move the emoji script to the runtime/tools directory.
98945560c1

src/nvim/testdir/test_functions.vim

@@ -1769,6 +1769,13 @@ func Test_char2nr()
   call assert_equal(12354, char2nr('あ', 1))
 endfunc
 
+func Test_charclass()
+  call assert_equal(0, charclass(' '))
+  call assert_equal(1, charclass('.'))
+  call assert_equal(2, charclass('x'))
+  call assert_equal(3, charclass("\u203c"))
+endfunc
+
 func Test_eventhandler()
   call assert_equal(0, eventhandler())
 endfunc