Verify that RTP17c, RTP17d and RTP17e are correctly implemented

[KacperKluka]

Problem As noticed in https://github.com/ably/ably-java/issues/760 the Java SDK still mentions RTP5c which has been transformed into RTP17c, RTP17d and RTP17e in recent versions of the features spec. The current implementation was written a long time ago and might not be up to date with the new requirements.

Solution We should make sure that the current implementation is aligned with the new requirements of the RTP17c, RTP17d and RTP17e. Also, all the mentions of RTP5c should be replaced with comments about the new requirements.

┆Issue is synchronized with this Jira Task by Unito

[KacperKluka]

This might also refer to the issue https://github.com/ably/ably-java/issues/397