Add message action bar for threaded events

[germain-gg]

Make sure we re-use the same message action bar as in the room timeline.

We will need to exclude some actions when an event is displayed in a thread context

I believe we need to exclude

• Reply to event
• Reply in thread

@janogarcia could you confirm whether anything else springs to mind

[janogarcia]

@gsouquet Regular replies wouldn't be excluded actually. Please refer to these two frames, where you can find examples of the popover menus for the different cases. 👍

03b Thread actions — The Thread Actions popover is revealed on click (root message and message author)
https://www.figma.com/file/T309ztx0sNyOOK6NKVLHsK/Threads?node-id=788%3A266820

03c Thread actions — The Thread Actions popover is revealed on click (non root message, no message author)
https://www.figma.com/file/T309ztx0sNyOOK6NKVLHsK/Threads?node-id=788%3A269782

[germain-gg]

What does the reply button do in that context then? Is it a shortcut to broadcast the answer to the main room timeline too?
Or do you expect to see the message replied to quoted in the thread view?

[janogarcia]

Oh, the second one. That is, keeping the ability to quote-reply to individual messages in a thread. Those replies would live within the context of the thread. If we ever add the ability to broadcast specific messages to the room timeline that would be a separate feature, unrelated to this one. 👍

[germain-gg]

Leaving the "reply" button out for now as the current thread's implementation does not allow you to have quote replies in the thread view, tracked as part of #19161