LibJS: Precompute the number of regs/constants/locals in Executable

Instead of doing it again on every call. Minor bump in call performance.

Libraries/LibJS/Bytecode/Executable.h

@@ -92,6 +92,8 @@ public:
     size_t number_of_registers { 0 };
     bool is_strict_mode { false };
 
+    size_t registers_and_constants_and_locals_count { 0 };
+
     struct ExceptionHandlers {
         size_t start_offset;
         size_t end_offset;

Libraries/LibJS/Bytecode/Generator.cpp

@@ -477,6 +477,8 @@ CodeGenerationErrorOr<GC::Ref<Executable>> Generator::compile(VM& vm, ASTNode co
     executable->argument_index_base = number_of_registers + number_of_constants + number_of_locals;
     executable->length_identifier = generator.m_length_identifier;
 
+    executable->registers_and_constants_and_locals_count = executable->number_of_registers + executable->constants.size() + executable->local_variable_names.size();
+
     generator.m_finished = true;
 
     return executable;

Libraries/LibJS/Runtime/ECMAScriptFunctionObject.cpp

@@ -507,7 +507,7 @@ ThrowCompletionOr<void> ECMAScriptFunctionObject::get_stack_frame_size(size_t& r
             executable = TRY(Bytecode::compile(vm(), *this));
         }
     }
-    registers_and_constants_and_locals_count = executable->number_of_registers + executable->constants.size() + executable->local_variable_names.size();
+    registers_and_constants_and_locals_count = executable->registers_and_constants_and_locals_count;
     argument_count = max(argument_count, formal_parameters().size());
     return {};
 }