LiveObject: Refactor public/internal classes with Objects prefix

[sacOO7]

• Prefix ObjectMessage.kt internal classes with *Objects prefix -> Update internal Objects interface names to have Object*/Objects* prefix specification#328
• Also, the use of LiveObject in the context of code is not recommended as per -> Add spec points to describe the Objects plugin specification#332 (comment)

┆Issue is synchronized with this Jira Task by Unito

[sacOO7]

• Rename LiveObjects interface to RealtimeObjects => Add spec points to describe the Objects plugin specification#332 (comment)
• Reference js PR -> https://github.com/ably/ably-js/pull/2043/files