Allow extensions to opt-out of reconnect in extension owned terminals

[TylerLeonhardt]

Does this issue occur when all extensions are disabled?: Yes/No

• VS Code Version: 1.57.0-insider
• OS Version: macOS

Steps to Reproduce:

1. Install PowerShell
2. Install PowerShell extension
3. Open a PowerShell file (this causes the "PowerShell Integrated Console" to open which is a terminal contributed by the PowerShell extension)
4. Close PowerShell file
5. Reload the window

Expected: No PowerShell Integrated Console (PSIC) to be restored (since an extension contributed it)
Actual: PSIC get's restored

Extra info:

Here's what they run:

vscode.window.createTerminal({
                name: this.title,
                shellPath: this.exePath,
                shellArgs: powerShellArgs,
                hideFromUser: !this.sessionSettings.integratedConsole.showOnStartup,
                cwd: this.sessionSettings.cwd
            });

https://github.com/PowerShell/vscode-powershell/blob/master/src/process.ts#L109-L115

[Tyriar]

I actually forgot about the decision I made here but it's coming back to me. I think the plan was to make an extension API to opt out of reconnect for extension owned terminals (it's always disabled using Pseudoterminal terminals). I think this makes the most sense as many extensions will create terminals and forget about them. I'll create an issue on the PS extension to look for and dispose of old reconnected terminals before starting up a new one.

Relevant code:

https://github.com/Microsoft/vscode/blob/baccddcd4599d72b834626ec08d20045ac031c20/src/vs/workbench/contrib/terminal/browser/terminalProcessManager.ts#L417-L417

[Tyriar]

PowerShell/vscode-powershell#3360