brightness: Add SetAmbientLightSensorEnabled to brightness delegate

this change), and confirmed that the feature works as expected

Test: ash_unittests --gtest_filter=*BrightnessControllerChromeosTest*
Test: Tested downstream CL crrev.com/c/5415325 on my DUT (which includes
Bug: b/328287584
Change-Id: I2e6e5887d4a0daff191a32fa126647aa7865c98d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5415913


Reviewed-by: David Padlipsky <dpad@google.com>
Reviewed-by: Wenyu Zhang <zhangwenyu@google.com>
Commit-Queue: Camden Bickel <cambickel@google.com>
Cr-Commit-Position: refs/heads/main@{#1281948}