Break up Menu/DefaultBuilder into functions that are reusable without
inheritance. The functions do not need much state to produce their
outputs and a weighty inheritance hierarchy makes the code difficult to
reason about. The functions are used in a following patch for the user
menu. They're now simple, independent, static functions in BuilderUtil
that are easy to reason about and compose.
Also, ban inheritance via `final` in a few places nearby. Inheritance
has not worked well in MobileFrontend and enabling it should be a
special deliberate case, not a default. E.g., in the user menu, the
changes could have been to the base class' getPersonalTools() method
such that the client passes a parameter for the advanced config or maybe
just override it in the subclass. In either case, it makes the whole
hierarchy nuanced and harder to reason about for something that should
be dead simple.
Bug: T214540
Change-Id: I6e9a2b36a1bff387eb3b33ea65b0a6806962810a
