Enable update status check by help page on MacOS

[simonhong]

• Delete Update Brave menu item (Enable help webui for checking update status and upgrade detector brave-core#271)
• Delete BraveAppControllerMac - move SUUpdaterDelegate impl to sparkle_glue (Enable help webui for checking update status and upgrade detector brave-core#271)
• Move sparkle related impl to brave/browser/mac
• Use webui as chrome does and don't use sparkle dialog
• Enable UpgradeDetector for MacOS
• Check how to get download/install progress info
• Try to remove passing --disable_brave_update in yarn test and check in runtime instead.

[bbondy]

Part needing QA:

• Delete Update Brave menu item (Enable help webui for checking update status and upgrade detector brave-core#271)

[kjozwiak]

Went through verification using the following build under macOS 10.13.6 x64 - PASSED

Brave	0.55.10 Chromium: 70.0.3538.22 (Official Build) beta(64-bit)
Revision	ac9418ba9c3bd7f6baaffa0b055dfe147e0f8364-refs/branch-heads/3538@{#468}
OS	Mac OS X