[vcpkg] Manifest Files

[strega-nil]

This is the tracking issue for manifest files!

• Add JSON parser: [vcpkg] Add initial JSON support #10521
• Get the manifest specification merged: [vcpkg] RFC: Manifests #11203
• Initial demo support for manifest files: strega-nil/vcpkg/manifest
• Full support for manifest files, behind a feature flag [vcpkg manifest] Manifest Implementation #11757
• Switch all CONTROL files to manifest files
• Remove the feature flag

[linquize]

You change CONTROL file to JSON format

[linquize]

Will support of CONTROL files be eventually removed?

[strega-nil]

@linquize probably at some point? but it's not in the plans yet.