Move common microfactory functions to cmd/microfactory/microfactory.bash
so that they can be used to build both soong_ui for normal build and
multiproduct_kati for build system tests.
Test: m -j
Test: build/soong/build_test.bash
Change-Id: I9512642d846ce54d05a027b6d33a2b3029b3f90b
