Resize terminal process after resizing widget

[Lythenas]

What it does

Fixes #13174

Resize the terminal process in the debounced doResizeTerminal (after the terminal widget has the new size) instead of directly in the onUpdateRequest.

Contributed on behalf of Elektrobit Automotive GmbH.

How to test

1. Start theia, open it in a browser
   • It's a bit inconsistent to reproduce, since it is a race condition. I found that setting a breakpoint on packages/terminal/src/browser/terminal-widget-impl.ts:604 (i.e. in onUpdateRequest) and stepping through always reproduces the issue.
2. Open a terminal
3. Run tput cols and tput lines, see that it is the incorrect size (defaults to 80 and 24, instead of the real size of the terminal widget after it is fix into the view)
4. Try to write a very long line, see that it wraps as 80 characters even though there is still space left
5. Resize the terminal (just wiggling is fine)
6. Do step 3 and 4 again and see that it now shows the correct size and behaves correctly

With this PR step 3 and 4 should behave correctly. I.e. the size of the terminal is correct after opening, without having to resize.

Follow-ups

Review checklist

• As an author, I have thoroughly tested my changes and carefully followed the review guidelines

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[msujew]

Thanks a lot for the fix @Lythenas 👍