Allow conhost to be replaced with OpenConsole

[lhecker]

Description of the new feature/enhancement

conhost can lack behind OpenConsole by several (if not many) years. This brings 2 problems:

• People preferring conhost's look and feel cannot get updates for many years.
• We (the maintainers) cannot test new features and changes for many years.

In other words, not being able to replace conhost is a lose-lose situation.

Proposed technical implementation details (optional)

• Ship a conhost package in the store that replaces the system conhost, just like how notepad does it.
• Consider doing the same for the Windows Terminal Canary package so that we can get a slightly better usage coverage.