runtime(vim): Update base-syntax, improve enum highlighting

Match enum values and missing class keywords.

fixes: #15970

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

runtime/syntax/testdir/input/vim9_ex_enum.vim

@@ -0,0 +1,111 @@
+vim9script
+# Vim :enum command
+# VIM_TEST_SETUP hi link vim9EnumValue Todo
+
+
+interface Interface1
+  def Def1()
+endinterface
+interface Interface2
+endinterface
+
+# enum-implements clause with interspersed comments
+
+enum Enum1 implements Interface1, Interface2
+  Value1
+  def Def1()
+  enddef
+endenum
+
+enum Enum2
+      \ implements Interface1, Interface2
+  Value1
+  def Def1()
+  enddef
+endenum
+
+enum Enum3 # comment
+      \ implements Interface1, Interface2
+  Value1
+endenum
+
+enum Enum4
+      # comment
+      \ implements Interface1, Interface2
+  Value1
+endenum
+
+enum Enum5
+      \ implements Interface1, Interface2 # comment
+  Value1
+  def Def1()
+  enddef
+endenum
+
+enum Enum6
+      #\ comment
+      \ implements Interface1, Interface2
+  Value1
+  def Def1()
+  enddef
+endenum
+
+# [enum Enum7.Value1 {name: 'Value1', ordinal: 0, val1: 0, val2: 0}, enum Enum7.Value2 {name: 'Value2', ordinal: 1, val1: 1, val2: 0}, enum Enum7.Value3 {name: 'Value3', ordinal: 2, val1: 2, val2: 0}]
+# comment
+enum Enum7
+      \
+      #\ comment
+      \
+      #\ comment
+      \ implements Interface1, Interface2 # comment
+    # comment
+    # comment
+    Value1,        # comment
+    # comment
+    # comment
+    Value2(1 + 0), # comment
+    # comment
+    # comment
+    Value3(   # comment
+      # comment
+      1       # comment
+        # comment
+        +     # comment
+      # comment
+      1       # comment
+    )         # comment
+    # comment
+    var val1: number # comment
+    # comment
+    def Def1()
+    enddef
+    # comment
+    static def Def2() # comment
+      # comment
+    enddef # comment
+    # comment
+    public var val2: number # comment
+endenum
+
+# [enum Enum8.implements {name: 'implements', ordinal: 0}]
+enum Enum8 implements Interface1, Interface2
+  implements
+  def Def1()
+  enddef
+endenum
+
+# [enum Enum9.Value1 {name: 'Value1', ordinal: 0, implements: 0}]
+enum Enum9 implements Interface1, Interface2
+  Value1
+  var implements: number
+  def Def1()
+  enddef
+endenum
+
+# [enum Enum10.implements {name: 'implements', ordinal: 0}]
+enum Enum10 implements Interface1, Interface2
+  implements
+  def Def1()
+  enddef
+endenum
+