follow-up(Forwarder) - minor enhancements:

[Antreesy]

follow-up from #10603:

• rename component to MessageForwarder
• fix <div class="forwarder"> style, as it's breaking MessageButtonBar appearance
• get rid of doubled usage of NcEmptyContent (was added here: 45cb031)
• check how openConversation method closes modal
• rework code, rename and cleanup methods and computed props
• make backportable changes

See screenshot attached:

Originally posted by @Antreesy in #10603 (comment)