Refactor `MessagesRead` response

[LiranCohen]

• Added entry to UnionMessageReply that represents response from MessagesRead.
• Modified MessagesReadReplyEntry to include data as a sibling property to message

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 98.69%. Comparing base (c6d8526) to head (d4cfba9).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #776 +/- ## ======================================= Coverage 98.69% 98.69% ======================================= Files 73 73 Lines 11257 11263 +6 Branches 1609 1609 ======================================= + Hits 11110 11116 +6 Misses 141 141 Partials 6 6 ```

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Have feedback on the report? Share it here.