Resend protocol messages for pending channels upon resume

[owenpearson]

• Resend respective ATTACH and DETACH messages for ATTACHING and DETACHING channels if connection is resumed (RTN19b)

[sync-by-unito]

➤ Automation for Jira commented:

The link to the corresponding Jira issue is https://ably.atlassian.net/browse/SDK-2882