Fix click-drag selection on an unfocused Terminal

[leonMSFT]

Summary of the Pull Request

This PR tries to address some of the weird interactions with pointer pressed events when the Terminal isn't in focus. Here's the four things that have changed as part of this PR;

1. This PR will allow the user to be able to make a selection with a click-drag without having to first perform a single click on a tab/pane to bring it to focus.
2. Another weird bug that's fixed in this PR is where trying to make a selection on an unfocused tab when it already has a selection active will simply extend the existing selection instead of making a new one.
3. Not related to the issue that his PR closes: a right click will now focus the tab/pane.

I've made sure that we still have the existing functionality where a single click on an unfocused tab/pane does not make a single-cell selection and just focuses the tab/pane.

PR Checklist

• Closes Behaviour of click-and-drag text selection depends inconsistently on prior pane and application focus state #4282
• CLA signed. If not, go over here and sign the CLA
• Tests added/passed

Validation Steps Performed

Played around with all sorts of selection when in-focus and out of focus with multiple panes and tabs.
Unit tests still pass as well.

[DHowett-MSFT]

Oh no! It looks like the line endings on TerminalControl.cpp got damaged, and github thinks the entire file has changed./

[DHowett-MSFT]

I love this. Do you have an idea how it'll interact with double-click selection? Can you double-click a word in an unfocused terminal and begin a chunked word selection?

[leonMSFT]

It won't chunk select if you perform a multi-click. It's because the way it's written now is that unless your first click is part of a click-drag selection, it will always only focus. So, even if you did a double click, the first click is a focus click, and the second click would be a single-character selection click.

I was actually considering whether to also let double click, triple click, and shift-click successfully select from out of focus, but for now I figured it might be simpler to only let the click-drag scenario through.

[DHowett-MSFT]

@carlos-zamora did you have any further concerns on this?

[DHowett-MSFT]

nit: before you merge this (by using the AutoMerge tag), please update the title to..

1. be "imperative"
2. be shorter than 72 characters

Pretend the title is the end of the sentence "If merged, this pull request will..."

[DHowett-MSFT]

(If you use the automerge tag, the bot will take the title and body of the PR as the commit title/body)

[ghost]

Hello @leonMSFT!

Because this pull request has the AutoMerge label, I will be glad to assist with helping to merge this pull request once all check-in policies pass.

p.s. you can customize the way I help with merging this pull request, such as holding this pull request until a specific person approves. Simply @mention me (@msftbot) and give me an instruction to get started! Learn more here.

[ghost]

🎉Windows Terminal Preview v0.9.433.0 has been released which incorporates this pull request.:tada:

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