Have zygote mount appcompat system properties

If needed, the zygote should mount
/dev/__properties__/appcompat_override in place of /dev/__properties__,
and reload system properties (and any constants derived from them)

Bug: 291814949
Test: atest AppcompatOverrideSystemPropertiesDeclarationTest

Change-Id: Ifd364f5d9463e88b2ee928c1f71a6b96b8c29f45
7 files changed