[LaTeX] Refactor braces contexts

Illustrate how `braces` are implemented in both TeX & LaTeX with same
content but different sub-scopes. Re-implementing a context without
meta_prepend/meta_append overrides it completely.

LaTeX/LaTeX.sublime-syntax

@@ -39,12 +39,17 @@ contexts:
   braces:
     - match: \{
       scope: punctuation.definition.group.brace.begin.latex
-      push:
-        - meta_scope: meta.group.brace.latex
-        - match: \}
-          scope: punctuation.definition.group.brace.end.latex
-          pop: true
-        - include: main
+      push: brace-group-body
+
+  brace-group-body:
+    - meta_scope: meta.group.brace.latex
+    - include: brace-group-end
+    - include: main
+
+  brace-group-end:
+    - match: \}
+      scope: punctuation.definition.group.brace.end.latex
+      pop: true
 
   # these are used to identify arguments in commands
   general-optional-arguments:

LaTeX/TeX.sublime-syntax

@@ -154,10 +154,17 @@ contexts:
   braces:
     - match: \{
       scope: punctuation.definition.group.brace.begin.tex
-      push:
-        - meta_scope: meta.group.brace.tex
-        - include: brace-group-end
-        - include: main
+      push: brace-group-body
+
+  brace-group-body:
+    - meta_scope: meta.group.brace.tex
+    - include: brace-group-end
+    - include: main
+
+  brace-group-end:
+    - match: \}
+      scope: punctuation.definition.group.brace.end.tex
+      pop: true
 
   # within macros, it is possible that only part of some nested struture
   # is present. To prevent this from causing problems, here we only match
@@ -383,12 +390,6 @@ contexts:
     - match: (?=\S)
       pop: true
 
-  # matches a closing brace and pops the context
-  brace-group-end:
-    - match: \}
-      scope: punctuation.definition.group.brace.end.tex
-      pop: true
-
   immediately-pop:
     - match: ''
       pop: true