[vscode] Support TerminalExitReason

[rschnekenbu]

What it does

Adds support for terminal exit status reason and TerminalExitReason enum

Fixes #12023

Contributed on behalf of STMicroelectronics

How to test

This PR adds a reason why the terminal view was closed. This may come from a user action (close buttton), from the process itself that was exited, from an extension or from tool shutdown.
Here is an extension based on vscode example with additional information on terminal window close event

vscode-terminal-api-example-0.0.1.zip

1. Testing close on user action

• open Command Palette...
• select Terminal API: Create Terminal
• select Terminal API: Show Terminal and select one terminal
• simply close terminal with 'X' button
• notification shall indicate 3 as exit reason (User value)

2. Testing close on process exit

• open Command Palette...
• select Terminal API: Create Terminal
• select Terminal API: Show Terminal and select one terminal
• type 'exit' in the terminal window
• notification shall indicate 2 as exit reason (Process value)

3. Testing close by extension

• open Command Palette...
• select Terminal API: Create Terminal
• select Terminal API: Show Terminal and select one terminal
• select Terminal API: Dispose and select one terminal
• notification shall indicate 4 as exit reason (Extension value)

I could not find a way to reproduce and to check shutdown reason.

Review checklist

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

Reminder for reviewers

• As a reviewer, I agree to behave in accordance with the review guidelines

[tsmaeder]

Looks good to me.