* Add type hints where possible.
* Add initialization values to properties where needed.
* Remove @var block if redundant to type declaration.
* Use single line /** @var type $var */ instead of multi line.
Change-Id: I35236c5c1a2abb49e8ea2da090df3d655206195f
Rather than hardcoding the icons for all our menu items
let's use the definitions in core.
This also makes it easier for us to deprecate the
MobileMenu hook in future.
Rejoice at all the code this removed!
Bug: T291568
Change-Id: I69b5ca13aee018982a5ea28677d4a37e663235d4
