Address compiler switch errors/warnings (ExecuteTorch) (pytorch#15543)

Summary:

Make improvements so that it is safe to use the `-Wswitch-enum` compiler error in a project consuming RN

Reviewed By: shoumikhin

Differential Revision: D86070193

Author: NSProgrammer

runtime/core/exec_aten/util/scalar_type_util.h

@@ -918,6 +918,7 @@ struct promote_types {
     const auto& _st = TYPE;                                    \
     constexpr const char* et_switch_name = NAME;               \
     (void)et_switch_name; /* Suppress unused var */            \
+    C10_DIAGNOSTIC_PUSH_AND_IGNORED_IF_DEFINED("-Wswitch-enum") \
     switch (_st) {                                             \
       __VA_ARGS__                                              \
       default:                                                 \
@@ -928,6 +929,7 @@ struct promote_types {
             ::executorch::runtime::toString(_st),              \
             et_switch_name);                                   \
     }                                                          \
+    C10_DIAGNOSTIC_POP()                                       \
   }()
 
 #define ET_INTERNAL_SWITCH_CASE_INT_TYPES(CTYPE_ALIAS, ...)            \