Ensure relative order of DAP messages and repl elements; #33822; #79196

[dgozman]

Three fixes:

• handle each DAP message in a separate task to ensure that all microtasks run in between;
• append repl elements in sequential order by chaining their async processing;
• fire onDidChangeREPLElements directly in ReplModel to ensure it is fired at the right time.

@isidorn What do you think about this approach? Seems to resolve all test cases for me:

• console.log([1, 2]); 3
• console.log([1, 2]); console.log(3); setTimeout(() => console.log(5), 0); 4
• setTimeout(() => console.log(5), 0); Array(1000).fill(0)

[isidorn]

@dgozman thanks for the PR.
Here's some inital feedback:

• There are conflicts with the master branch which make it harder for me to nicely review this
• As you mention this PR seems to do multiple things, thus increasing its complexity. Could we maybe seperate this PR into smaller PRs so it is easier for us to review and merge. If the separate parts make sense on their own of course
• I do not like that the repl events is now half half fired from the model and from the session. Can we move everything to the model? And the sesssion just re-exposes that event? Probably the addReplExpression will aslo need to fire on the session side, but that can be the only corner case
• Handling all the DAP messages with a timeout of 0 feels a bit like a hack to me, and just out of luck works. I might be wrong, but I would like if we get that as an independent PR.
• Instead of using slots it might be easier to use some of our async utilites. Maybe the Sequencer is what you are looking for. There is other cool stuff there.

Thanks again and let me know what you think about my feedback.

[isidorn]

Since you have created separate PRs I will close this one. Hope that is ok.