Bulk convert control files. (#19986)

```
function Convert-Control {
    Param($full)
    .\vcpkg.exe format-manifest $full
    $root = $full.Substring(0, $full.Length - 7) # CONTROL
    $new = $root + 'vcpkg.json'
    $content = Get-Content -Raw $new
    $asJson = ConvertFrom-Json $content -AsHashtable -Depth 100
    $oldVersion = $asJson['port-version']
    if ($null -eq $oldVersion) {
        $oldVersionFull = $asJson['version-string']
        Write-Host "Got version $oldVersionFull"
        $match = [System.Text.RegularExpressions.Regex]::Match($oldVersionFull, '^(.+)-(\d+)$')
        if ($match.Success -and -not [System.Text.RegularExpressions.Regex]::IsMatch($oldVersionFull, '^\d\d\d\d-\d\d-\d\d$')) {
            $newFullVersion = [string]$match.Groups[1].Value
            $oldVersion = [int]$match.Groups[2].Value
            Write-Host "newFullVersion $newFullVersion oldVersion $oldVersion"
            $newVersion = $oldVersion + 1
            $asJson['version-string'] = $newFullVersion
            Write-Host "Previous version for $full extracted from version field -- setting version-string $newFullVersion and port-version $newVersion"
        } else {
            Write-Host "No previous version for $full -- setting 1"
            $newVersion = 1
        }
    } else {
        $newVersion = [int]$oldVersion + 1
        Write-Host "New version for $full : $newVersion"
    }

    $asJson['port-version'] = $newVersion

    $content = ConvertTo-Json $asJson -Depth 100
    Set-Content -Path $new -Value $content
    .\vcpkg.exe format-manifest $new
}

Get-ChildItem ports\CONTROL -Recurse | Foreach-Object {
    Convert-Control $_.FullName
}

git commit -am "this message"
.\vcpkg.exe x-add-version -all
git commit -a --amend
```

2 files changed, 80 insertions, 48 deletions

diff --git a/ports/mathgl/CONTROL b/ports/mathgl/CONTROL
deleted file mode 100644
index 7dc82d3f9..000000000
--- a/ports/mathgl/CONTROL
+++ /dev/null
@@ -1,48 +0,0 @@
-Source: mathgl
-Version: 2.4.3-6
-Description: MathGL is a free library of fast C++ routines for the plotting of the data varied in one or more dimensions
-Default-Features: opengl, jpeg, png, zlib
-
-Feature: hdf5
-Build-Depends: hdf5
-Description: hdf5 module
-
-Feature: fltk
-Build-Depends: fltk
-Description: fltk module
-
-Feature: gif
-Build-Depends: giflib
-Description: gif module
-
-Feature: png
-Build-Depends: libpng
-Description: png module
-
-Feature: zlib
-Build-Depends: zlib
-Description: zlib module
-
-Feature: jpeg
-Build-Depends: libjpeg-turbo
-Description: jpeg module
-
-Feature: gsl
-Build-Depends: gsl
-Description: gsl module
-
-Feature: opengl
-Build-Depends: opengl
-Description: opengl module
-
-Feature: glut
-Build-Depends: freeglut
-Description: glut module
-
-Feature: wx
-Build-Depends: wxwidgets
-Description: wx module
-
-Feature: qt5
-Build-Depends: qt5
-Description: qt5 module
diff --git a/ports/mathgl/vcpkg.json b/ports/mathgl/vcpkg.json
new file mode 100644
index 000000000..f3bfc67fa
--- /dev/null
+++ b/ports/mathgl/vcpkg.json
@@ -0,0 +1,80 @@
+{
+  "name": "mathgl",
+  "version-string": "2.4.3",
+  "port-version": 7,
+  "description": "MathGL is a free library of fast C++ routines for the plotting of the data varied in one or more dimensions",
+  "default-features": [
+    "jpeg",
+    "opengl",
+    "png",
+    "zlib"
+  ],
+  "features": {
+    "fltk": {
+      "description": "fltk module",
+      "dependencies": [
+        "fltk"
+      ]
+    },
+    "gif": {
+      "description": "gif module",
+      "dependencies": [
+        "giflib"
+      ]
+    },
+    "glut": {
+      "description": "glut module",
+      "dependencies": [
+        "freeglut"
+      ]
+    },
+    "gsl": {
+      "description": "gsl module",
+      "dependencies": [
+        "gsl"
+      ]
+    },
+    "hdf5": {
+      "description": "hdf5 module",
+      "dependencies": [
+        "hdf5"
+      ]
+    },
+    "jpeg": {
+      "description": "jpeg module",
+      "dependencies": [
+        "libjpeg-turbo"
+      ]
+    },
+    "opengl": {
+      "description": "opengl module",
+      "dependencies": [
+        "opengl"
+      ]
+    },
+    "png": {
+      "description": "png module",
+      "dependencies": [
+        "libpng"
+      ]
+    },
+    "qt5": {
+      "description": "qt5 module",
+      "dependencies": [
+        "qt5"
+      ]
+    },
+    "wx": {
+      "description": "wx module",
+      "dependencies": [
+        "wxwidgets"
+      ]
+    },
+    "zlib": {
+      "description": "zlib module",
+      "dependencies": [
+        "zlib"
+      ]
+    }
+  }
+}