This refactoring prepares for introduction of bazel prod mode, an
alternative mechanism for mixed builds allowlist handling.
* Decide bazel-mode as close to soong_build main as possible
* BazelContext itself decides whether a module is allowlisted
* Separate bp2build and mixed build allowlist
Test: m nothing, manually verified all modules are mixed build disabled
(via metrics)
Test: USE_BAZEL_ANALYSIS=1 m nothing, manually verified that mixed build
disabled/enabled modules are identical before and after change.
Change-Id: I0f55d8b85000cb4a871a099edc6d7d868d7df509
ad876010fe