Make load argument of native-compile-async internal

* lisp/emacs-lisp/comp.el (native--compile-async): New defun extracted
from native-compile-async.
(native-compile-async): Remove load argument and use above new defun.
* src/comp.c (maybe_defer_native_compilation): Use above new
defun.  (Bug#44676)
4 jobs for feature/native-comp in 225 minutes and 27 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Test
failed #8918
test-all

00:00:03

passed #8919
test-native-bootstrap-speed0

03:45:27

passed #8920
test-native-bootstrap-speed1

02:37:15

passed #8921
test-native-bootstrap-speed2

02:41:47

 
Name Stage Failure
failed
test-all Test There has been a runner system failure, please try again
Running with gitlab-runner 11.6.0 (f100a208)
on emba-docker-runner 2oEDrUT7
Using Docker executor with image debian:stretch ...
Pulling docker image debian:stretch ...
Using docker image sha256:b33ba41eae78980b0cd524b0d80983ac11025f6c5f2776ed4a861c9d5f805ede for debian:stretch ...
Running on runner-2oEDrUT7-project-1-concurrent-0 via emba.gnu.org...
ERROR: Job failed (system failure): Error response from daemon: No such container: 57b429ffd923185b940561945e082b8c1b180facc5619dc7ff974ca156f955ef (executor_docker.go:924:0s)