Cleanup: move public doc-strings into headers for 'bmesh'

Some minor improvements to doc-strings too.

Ref T92709

source/blender/bmesh/operators/bmo_create.c

@@ -31,12 +31,11 @@
 #define ELE_NEW 1
 #define ELE_OUT 2
 
-/* This is what runs when pressing the F key
- * doing the best thing here isn't always easy create vs dissolve, its nice to support
- * but it _really_ gives issues we might have to not call dissolve. - campbell
- */
 void bmo_contextual_create_exec(BMesh *bm, BMOperator *op)
 {
+  /* NOTE(@campbellbarton): doing the best thing here isn't always easy create vs dissolve,
+   * its nice to support but it _really_ gives issues we might have to not call dissolve. */
+
   BMOIter oiter;
   BMHeader *h;
   int totv = 0, tote = 0, totf = 0;