Introduces a new prop and turns it off by default.
Also rewrites the initial "all applications" data gathering avoid
a crash uncovered while working on this (it didn't check EntryType)
and reduces assumptions about the model topology.
It also makes it collect root-level apps now, which was forgotten
to be added when support for root-level apps were added.
This supercedes D22762 and D22890. It does less duplicate work and fixes
more bugs.