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, 62 insertions, 24 deletions

diff --git a/ports/libssh/CONTROL b/ports/libssh/CONTROL
deleted file mode 100644
index cec23294e..000000000
--- a/ports/libssh/CONTROL
+++ /dev/null
@@ -1,24 +0,0 @@
-Source: libssh
-Version: 0.9.5
-Port-Version: 5
-Homepage: https://www.libssh.org/
-Build-Depends: libssh[core,mbedtls] (android)
-Description: libssh is a multiplatform C library implementing the SSHv2 protocol on client and server side
-Default-Features: crypto
-Supports: !(uwp | arm)
-
-Feature: crypto
-Build-Depends: libssh[mbedtls]
-Description: Default crypto backend
-
-Feature: mbedtls
-Build-Depends: mbedtls[pthreads] (!android), mbedtls[core]
-Description: Crypto support (mbedTLS)
-
-Feature: openssl
-Build-Depends: openssl
-Description: Crypto support (OpenSSL)
-
-Feature: zlib
-Description: libssh with zlib
-Build-Depends: zlib
diff --git a/ports/libssh/vcpkg.json b/ports/libssh/vcpkg.json
new file mode 100644
index 000000000..47669c5a2
--- /dev/null
+++ b/ports/libssh/vcpkg.json
@@ -0,0 +1,62 @@
+{
+  "name": "libssh",
+  "version-string": "0.9.5",
+  "port-version": 6,
+  "description": "libssh is a multiplatform C library implementing the SSHv2 protocol on client and server side",
+  "homepage": "https://www.libssh.org/",
+  "supports": "!(uwp | arm)",
+  "dependencies": [
+    {
+      "name": "libssh",
+      "default-features": false,
+      "features": [
+        "mbedtls"
+      ],
+      "platform": "android"
+    }
+  ],
+  "default-features": [
+    "crypto"
+  ],
+  "features": {
+    "crypto": {
+      "description": "Default crypto backend",
+      "dependencies": [
+        {
+          "name": "libssh",
+          "features": [
+            "mbedtls"
+          ]
+        }
+      ]
+    },
+    "mbedtls": {
+      "description": "Crypto support (mbedTLS)",
+      "dependencies": [
+        {
+          "name": "mbedtls",
+          "default-features": false
+        },
+        {
+          "name": "mbedtls",
+          "features": [
+            "pthreads"
+          ],
+          "platform": "!android"
+        }
+      ]
+    },
+    "openssl": {
+      "description": "Crypto support (OpenSSL)",
+      "dependencies": [
+        "openssl"
+      ]
+    },
+    "zlib": {
+      "description": "libssh with zlib",
+      "dependencies": [
+        "zlib"
+      ]
+    }
+  }
+}