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, 66 insertions, 27 deletions

diff --git a/ports/libigl/CONTROL b/ports/libigl/CONTROL
deleted file mode 100644
index bec096774..000000000
--- a/ports/libigl/CONTROL
+++ /dev/null
@@ -1,27 +0,0 @@
-Source: libigl
-Version: 2.2.0
-Port-Version: 5
-Homepage: https://github.com/libigl/libigl
-Description: libigl is a simple C++ geometry processing library. We have a wide functionality including construction of sparse discrete differential geometry operators and finite-elements matrices such as the cotangent Laplacian and diagonalized mass matrix, simple facet and edge-based topology data structures, mesh-viewing utilities for OpenGL and GLSL, and many core functions for matrix manipulation which make Eigen feel a lot more like MATLAB.
-Build-Depends: eigen3
-Supports: !(arm|uwp)
-
-Feature: embree
-Description: Build with embree
-Build-Depends: embree3
-
-Feature: opengl
-Description: Build with opengl
-Build-Depends: opengl, glad
-
-Feature: glfw
-Description: Build with glfw
-Build-Depends: libigl[core, opengl], glfw3
-
-Feature: imgui
-Description: Build with imgui
-Build-Depends: libigl[core, glfw], imgui[core, glfw-binding, opengl3-binding, libigl-imgui]
-
-Feature: xml
-Description: Build with libxml
-Build-Depends: tinyxml2
diff --git a/ports/libigl/vcpkg.json b/ports/libigl/vcpkg.json
new file mode 100644
index 000000000..2a4a9797d
--- /dev/null
+++ b/ports/libigl/vcpkg.json
@@ -0,0 +1,66 @@
+{
+  "name": "libigl",
+  "version-string": "2.2.0",
+  "port-version": 6,
+  "description": "libigl is a simple C++ geometry processing library. We have a wide functionality including construction of sparse discrete differential geometry operators and finite-elements matrices such as the cotangent Laplacian and diagonalized mass matrix, simple facet and edge-based topology data structures, mesh-viewing utilities for OpenGL and GLSL, and many core functions for matrix manipulation which make Eigen feel a lot more like MATLAB.",
+  "homepage": "https://github.com/libigl/libigl",
+  "supports": "!(arm | uwp)",
+  "dependencies": [
+    "eigen3"
+  ],
+  "features": {
+    "embree": {
+      "description": "Build with embree",
+      "dependencies": [
+        "embree3"
+      ]
+    },
+    "glfw": {
+      "description": "Build with glfw",
+      "dependencies": [
+        "glfw3",
+        {
+          "name": "libigl",
+          "default-features": false,
+          "features": [
+            "opengl"
+          ]
+        }
+      ]
+    },
+    "imgui": {
+      "description": "Build with imgui",
+      "dependencies": [
+        {
+          "name": "imgui",
+          "default-features": false,
+          "features": [
+            "glfw-binding",
+            "libigl-imgui",
+            "opengl3-binding"
+          ]
+        },
+        {
+          "name": "libigl",
+          "default-features": false,
+          "features": [
+            "glfw"
+          ]
+        }
+      ]
+    },
+    "opengl": {
+      "description": "Build with opengl",
+      "dependencies": [
+        "glad",
+        "opengl"
+      ]
+    },
+    "xml": {
+      "description": "Build with libxml",
+      "dependencies": [
+        "tinyxml2"
+      ]
+    }
+  }
+}