fix: "no_apex" can be put in defaults

Currently, putting no_apex in defaults module doesn't work.

To fix this,
* 'no_apex' property is added as 'defaultable'.
* apex module doesn't follow beyond 'defaults' module.

Bug: 141560644
Test: m (soong tests added)
Change-Id: I8410785f7f83d843689a33b1241d74086c6a7671