Make all defaults modules bazelable

Since these are not being converted directly, this has two primary
impacts:
* defaults modules will no longer appear as unconverted deps.
* defaults modules do not have to be marked individually, which should
  allow all defaults-based soong-config-modules to just convert as
  necessary.

Test: bp2build.sh
Change-Id: I44c99d5a51d1887a95c17dfdf956f91af671b2ea