Allow identifying who is currently typing in a shared terminal

[lostintangent]

Currently, when you share a terminal in read-write mode, all participants are sharing a single cursor for that terminal, as opposed to the multi-cursor support that we support for file editing (command line tools aren't built to support concurrent streams of input). However, unlike file editing, there is no way to identity who is currently "in" the terminal, and furthermore, who is typing. For 1:1 scenarios, this isn't as critical (since you'd know who is typing), but when doing mob programming (for example), this would become very important context to know.

Additionally, as part of this, we should ensure that when you follow another participant, and they move to a terminal instance, that your focus follows them there as well. This is somewhat related to #185, but would likely require UI within the terminal, as opposed to the project-wide proposal that #185 discusses.

[lostintangent]

@IlyaBiryukov FYI, this was a request from a user, and is inline with some thinking we had around improving user presence for terminals.

[IlyaBiryukov]

We can associate terminal input with the user who produced it, the question is, how to visually display that. We'd need some UI support from xterm control, and then we'd need to convince Whack Whack and VSCode to use the updated xterm. Furthermore, when I checked if Whack Whack works with latest version of xterm, I saw it was much slower, so there may be some work to investigate that too.

[lostintangent]

@IlyaBiryukov Yep agreed. We need to do some design work before this is "shovel ready". I just wanted to give you an FYI, as this is something we may discuss in the future, depending on additional user feedback.

[lostintangent]

I'm going to close this for now since we haven't heard significant customer feedback for this, and I'm the one who opened it 😄 If this is something that folks would like to see us prioritize, please let us know by re-opening/commenting on this bug. Thanks!