[docs] Rewrite doc for vcpkg_cmake_configure. Move up into docs/maintainers/.

[ras0219-msft]

This is the first docs overhaul PR for a helper function from a port.

A key change I propose for the port-based helpers is to de-segregate them from the "built-in" helpers and instead rely on documentation within the page to guide users on how to consume it. This change accomplishes two goals:

1. Improve discoverability - All helper functions (built-in + curated catalog) will be findable in the same location, so users don't need to look in multiple places.
2. Improve usefulness - By including the usage syntax to depend upon the providing port, users have a "one-stop shop" to answer the common scenario of "I was told to use X, how do I do that?".

[ras0219-msft]

Should these be merged into the list above?

[vicroms]

In my opinion, yes

[vicroms]

LGTM after the minor change I suggested.