[apkverify] Merge idsig into apkverify package

This CL merges idsig into apkverify package as apkverify is
supposed to cover apk signature verification v3 and v4.

Bug: 248999133
Test: libapkverify.test apkdmverity.test microdroid_manager_test
Change-Id: Ieef2dcf93496164f8bb72cd4ee819ebb822f6142
diff --git a/libs/apkverify/src/lib.rs b/libs/apkverify/src/lib.rs
index 1e0bd77..359d963 100644
--- a/libs/apkverify/src/lib.rs
+++ b/libs/apkverify/src/lib.rs
@@ -18,6 +18,7 @@
 
 mod algorithms;
 mod bytes_ext;
+mod hashtree;
 mod sigutil;
 #[allow(dead_code)]
 pub mod testing;
@@ -27,4 +28,4 @@
 
 pub use algorithms::SignatureAlgorithmID;
 pub use v3::{get_public_key_der, verify};
-pub use v4::get_apk_digest;
+pub use v4::{get_apk_digest, HashAlgorithm, V4Signature};