TDF and TDF script changes (application changes pending):

- Added new `pad` element to TDFs
- Refactored `pin` and `signal` elements to accommodate new `pad` element
- Improved validation of signal-to-pad relation in TDF validation script
- Added key attribute to `variant` element
- Removed `package` attribute from `variant` element

build/scripts/Targets/TargetDescriptionFiles/Signal.php

@@ -3,20 +3,20 @@ namespace Targets\TargetDescriptionFiles;
 
 class Signal
 {
-    public ?string $padId = null;
+    public ?string $padKey = null;
     public ?int $index = null;
     public ?string $function = null;
     public ?string $group = null;
     public ?string $field = null;
 
     public function __construct(
-        ?string $padId,
+        ?string $padKey,
         ?int $index,
         ?string $function,
         ?string $group,
         ?string $field
     ) {
-        $this->padId = $padId;
+        $this->padKey = $padKey;
         $this->index = $index;
         $this->function = $function;
         $this->group = $group;