[apk_digest] Return SignatureAlgorithmID when fetching apk digest

This CL changes the apk digest fetch API's return type from raw
integer to SignatureAlgorithmID enum. This API is used in avmd
and idsig.

Bug: 246254355
Test: avmdtool_tests libidsig.test libapkverify.test
Change-Id: I4aba18e22324f74af328115a6cadd718eb45f220
diff --git a/libs/apkverify/Android.bp b/libs/apkverify/Android.bp
index 9bb8f8e..78192d2 100644
--- a/libs/apkverify/Android.bp
+++ b/libs/apkverify/Android.bp
@@ -15,6 +15,7 @@
         "liblog_rust",
         "libnum_traits",
         "libopenssl",
+        "libserde",
         "libzip",
     ],
     proc_macros: ["libnum_derive"],