Add extension support for view-level progress indicators

[eamodio]

Refs: #92135

Now that we can support view-level progress indicators, we should expose this ability to extensions.

Current proposal:

vscode/src/vs/vscode.proposed.d.ts

Lines 1828 to 1845 in eb4ebee

	//#region https://github.com/microsoft/vscode/issues/92421
	export enum ProgressLocation {
	/**
	* Show progress for a view, as progress bar inside the view (when visible),
	* and as an overlay on the activity bar icon. Doesn't support cancellation or discrete progress.
	*/
	View = 25,
	}
	export interface ProgressOptions {
	/**
	* The target view identifier for showing progress when using [ProgressLocation.View](#ProgressLocation.View).
	*/
	viewId?: string
	}
	//#endregion

Alternative # 1:

export interface ProgressOptions {
    location: ProgressLocation | string;
}

Alternative # 2:

export interface ProgressOptions {
    location: ProgressLocation | { viewId: string };
}

//cc @jrieken

[eamodio]

I think I prefer alt #2, but I chose the first, because neither alt 1 or 2 can be implemented in vscode.proposed.d.ts

[eamodio]

Alternative # 2 above implemented:

vscode/src/vs/vscode.d.ts

Lines 7938 to 7958 in d778f85

	export interface ProgressOptions {
	/**
	* The location at which progress should show.
	*/
	location: ProgressLocation | { viewId: string };
	/**
	* A human-readable string which will be used to describe the
	* operation.
	*/
	title?: string;
	/**
	* Controls if a cancel button should show to allow the user to
	* cancel the long running operation. Note that currently only
	* `ProgressLocation.Notification` is supporting to show a cancel
	* button.
	*/
	cancellable?: boolean;
	}