global: Cleanup line lengths and misc lint warnings

I know we decided to ditch the idea of shutting up "Exception
thrown with empty param" warnings but this pesters me too
much and we can instead just treat this as a weird future proofing
thing if and when we end up needing the exception messages.

Signed-off-by: Harsh Shandilya <me@msfjarvis.dev>

app/src/main/java/com/wireguard/config/IPCidr.java

@@ -15,6 +15,7 @@ public class IPCidr {
     private final InetAddress address;
     private int cidr;
 
+    @SuppressWarnings("MagicNumber")
     public IPCidr(String in) {
         cidr = -1;
         final int slash = in.lastIndexOf('/');