Everywhere: Convert ByteBuffer factory methods from Optional -> ErrorOr

Apologies for the enormous commit, but I don't see a way to split this
up nicely. In the vast majority of cases it's a simple change. A few
extra places can use TRY instead of manual error checking though. :^)

AK/Base64.cpp

@@ -97,7 +97,7 @@ Optional<ByteBuffer> decode_base64(StringView input)
             output.append(out2);
     }
 
-    return ByteBuffer::copy(output);
+    return ByteBuffer::copy(output).release_value_but_fixme_should_propagate_errors();
 }
 
 String encode_base64(ReadonlyBytes input)