[RFC][registries] Allow pattern matching in packages declarations

[vicroms]

This PR makes the following changes to allow limited pattern matching for package declarations in registries:

• Allow prefixes in the form foo* in "packages" declarations.
• The * character is a wildcard that matches any zero or more characters.
• The port name resolution priority will change to:
  1. Exact match
  2. Pattern match
     1. Longer prefixes have higher priority, e.g.: when resolving boost, boost* > b* > *.
     2. If there is a tie, we use the registry that is declared first in the "packages" array.
        A warning will be emitted to notify the user of possible misconfiguration.
  3. Default registry

Example: expose "beicode" and "beison" via patterns.

vcpkg-configuration.json

{
  "registries": [
    {
      "kind": "git", 
      "repository": "https://github.com/northwindtraders/vcpkg-registry", 
      "baseline": "dacf4de488094a384ca2c202b923ccc097956e0c", 
      "packages": [ "bei*" ] 
    }
  ]
}

Checklist:

• Changes to port name resolution logic
  • Implement resolution priority
  • Implement warning on masked registries
• Change configuration parser
• Unit tests
• Documentation (PR [RFC][docs] Add pattern matching docs vcpkg#27686)

[Neumann-A]

oh no. If this is implemented please also add an exclusion list ...

[BillyONeal]

oh no. If this is implemented please also add an exclusion list ...

The "exclusion list" is adding the excluded thing to the registry you actually want used.

[BillyONeal]

"Request changes" over the threading concerns in making the serializers mutable. Other changes are suggestions.

[Neumann-A]

The "exclusion list" is adding the excluded thing to the registry you actually want used.

Should be documented.

[vicroms]

The "exclusion list" is adding the excluded thing to the registry you actually want used.

Should be documented.

I've added an example in the docs PR.