apkverify: Re-export functions rather than wrap them

The library exposes two functions that are just wrappers around the v3
implementation. Make that more clear by simply re-exporting the v3
functions. The TODO for adding v2 support remains.

The documentation is consolidated so the same information remains.

Test: atest libapkverify.test
Change-Id: Id497486dd054474516a664be1539b41732085b79
diff --git a/libs/apkverify/src/v3.rs b/libs/apkverify/src/v3.rs
index 797911b..eb12498 100644
--- a/libs/apkverify/src/v3.rs
+++ b/libs/apkverify/src/v3.rs
@@ -87,7 +87,7 @@
 type AdditionalAttributes = Bytes;
 
 /// Verifies APK Signature Scheme v3 signatures of the provided APK and returns the public key
-/// associated with the signer.
+/// associated with the signer in DER format.
 pub fn verify<P: AsRef<Path>>(path: P) -> Result<Box<[u8]>> {
     let f = File::open(path.as_ref())?;
     let mut sections = ApkSections::new(f)?;