[🚀 Request] Enable installation of pre-release version of extension to the test instance

[serhergz]

Describe the request

Enable the CLI to allow the install pre-release version of extensions to the test instance, when they are available in the market place. This functionality is already present in the CLI of VSC.

Usage

When developing an extension which depends on third party extensions, it is necessary to periodically test against early versions of those dependencies, and identify changes that could generate problem and have react before they are release. Automating this kind of test allows to execute them easily and periodically.
Example of proposed usage:
extest install-from-marketplace ms-vscode.cpptools --pre_release