Switch recovery to versioned policy and split into components.

And do some clean up:
Replace LOCAL_TARGET_ARCH with global arch specifier that won't get
clobbered, clean up sepolicy.recovery's eng specification, ensure that
build macros are applied across all policy generation, not just
plat_policy, and make sure that all private variables are cleared and
alphabetized at the end.

Bug: 31363362
Bug: 31369363
Test: Boot into recovery and observe no selinux denials.
Change-Id: Ibc15b097f6d19acf01f6b22bee0e083b15f4ef75