Flaky realtime tests for RealtimeChannelTest

[sacOO7]

• Consistent failing integration tests for RealtimeChannelTest are being observed.
• Tests seem to be working on local, so flakiness is mostly observed on the CI.
• Cause mostly seems to be recent merged PR [ECO-5163] fix: duplicated messages because of duplicated attach message #1052.
• Aim to remove CI flakiness for all RealtimeChannelTest.java tests.

┆Issue is synchronized with this Jira Task by Unito

[sacOO7]

Following are flaky tests

• 1. io.ably.lib.test.realtime.RealtimeResumeTest.resume_rewind_1[binary_protocol] FAILED
• 2. io.ably.lib.test.realtime.RealtimeChannelTest > channel_server_initiated_detached[text_protocol] FAILED
• 3. io.ably.lib.test.realtime.RealtimeChannelTest > channel_reattach_failed_timeout[text_protocol] FAILED
• 4. io.ably.lib.test.realtime.RealtimeChannelTest > channel_reattach_failed_error[text_protocol] FAILED