librpcbinder_rs: enable use in Minidroid RPC sample

This CL adds visibility and //apex_available:platform needed to make a
Rust variant of a Minidroid RPC sample app build (aosp/2402014).

Other visibility entries are added to ensure the APEXes already enabled
via `apex_available` keep compiling. There's 8 subpackages of
`//packages/modules/Virtualization` that use librpcbinder_rs, so I used
`__subpackages__` instead of listing each one. This covers visibility
for both `com.android.virt` and `com.android.compos` APEXes.

Test: * m client_minidroid_rust with aosp/2402014 patched in
      * m com.android.compos com.android.uwb com.android.virt
Change-Id: Ie67f450cbc8b5d93be5dbcf0eb8c782ee26c2b45