IPC: add status streaming support

This adds a NOTIFY_STREAM command to the ctrl interface, this
is implemented with a history replay functionality so that
clients can see notify messages from before they connect.

This has the advantage of making it possible for multiple clients
to monitor notify messages at the same time.

Signed-off-by: James Hilliard <james.hilliard1@gmail.com>
1 job for master in 6 minutes and 45 seconds (queued for 4 seconds)
Status Name Job ID Coverage
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passed ubuntu-focal #326722

00:06:45