Support message edits and deletes

[sacOO7]

• Related spec PRs ->

1. https://github.com/ably/specification/pull/210/files
2. https://github.com/ably/specification/pull/263/files
3. https://github.com/ably/specification/pull/235/files

• Related chat spec PRs ->

1. https://github.com/ably/specification/pull/266/files
2. https://github.com/ably/specification/pull/216/files

• Implemention is mostly related to the change in TM* fields

┆Issue is synchronized with this Jira Task by Unito

[sacOO7]

Reference ably-js PRs

1. https://github.com/ably/ably-js/pull/1945/files
2. https://github.com/ably/ably-js/pull/1916/files
3. https://github.com/ably/ably-js/pull/1888/files

[sacOO7]

TODOs
Add following missing fields to message as per TM2l, TM2m, TM2n

• 1. TM2l = refSerial string – an opaque string that uniquely identifies some referenced message.
• 2. TM2m = refType string – an opaque string that identifies the type of this reference.
• 3. TM2n = operation – object that may contain the following optional attributes.
• 4. Add message create, update and delete tests for the same to check if fields are being populated correctly and hence received accordingly. Reference message create, update and delete operations => API described here -> https://sdk.ably.com/builds/ably/specification/main/chat-features/