android.sdk aconfig flags: add android.sdk.flags-aconfig-java-host

Add a new soong host module for the android.sdk aconfig flags. This
module will be used by CTS host tests.

Bug: 377689343
Test: treehugger
Flag: EXEMPT no need to flag changes to flags themselves
Change-Id: I8d1e0c39ab4c9129ed0238ba1ccf08fa29f6efd1