Description of the new feature/enhancement

Today, to get to the command line mode I need to open the action mode and then to delete a ">" symbol, which is not very convenient.

While discussing this with @zadjii-msft few ideas were raised:

1. Adding a separate binding for ToggleCommandPalette(mode=commandline)
2. Having ToggleCommandPalette() switch between modes: closed->action->command line->closed.
3. Both of them ☺️

Proposed technical implementation details (optional)

The most straightforward solution is to add an optional command palette mode to the ToggleCommandPalette, with two "launch modes": action and command line.

We will be able to implement option 2 only once #8044 gets merged.