Existing bootstrap code in the wild depends on the existence of
.ngfactory files, which Ivy does not need. This commit adds the
capability in ngtsc to generate .ngfactory files which bridge
existing bootstrap code with Ivy.
This is an initial step. Remaining work includes complying with
the compiler option to specify a generated file directory, as well
as presumably testing in g3.
PR Close#25176
0822dc70f2