Make vndk*.libraries.txt as soong modules

Migrating from Make to Soong.

These files are generated by singleton and had to be defined as PREBUILT
modules in Make (system/core/rootdir/Android.mk)

Now, they are converted as soong modules.

To make things easier, a special kind of module 'vndk_libraries_txt' is
added which works like prebuilt_etc but its src file is generated by
soong.

Bug: 141450808
Test: m llndk.libraries.txt
Change-Id: Ia77e6af73f760fcd77020218c5bc37892b2cda1f