After successful bytecode compilation, the m_functions_to_initialize
and m_var_names_to_initialize_binding vectors are no longer needed
as they are only consumed by emit_function_declaration_instantiation()
during code generation.
Add clear_compile_inputs() to release these vectors post-compile,
and call it from both ECMAScriptFunctionObject::get_stack_frame_size()
and NativeJavaScriptBackedFunction::bytecode_executable() after their
respective lazy compilation succeeds.
Also add a pre-compile assertion in Generator::generate_from_function()
to verify we never try to compile the same function data twice, and a
VERIFY in ECMAScriptFunctionObject::ecmascript_code() to guard against
null dereference.