TGA: Support for TGA specification 2.0

Adds TGA 2.0 compliance:
- Support for Extension Area, Developer Area and Footer (metadata support)
- Support for 15-bit and 16-bit per pixel images (both RGB and Indexed)
- Full support for rotation on reading (we cannot use Qt transformations because only a subset is part of the TGA specification)
- When writing you can choose the supported version (subType)
- Improved writing speed (approximately 10 times) and removed whole image conversions (significant memory savings)

It pass the [TrueVision TGA 2.0 conformance suite](https://github.com/zigimg/test-suite/tree/master/fixtures/tga).

Test changes:
- Read test: added ability to skip a specific test on sequential devices (via JSON behavior file)
- Write test: added the ability to set the subType when writing (via JSON properties file)

Closes #37

autotests/write/basic/tga.json

@@ -0,0 +1,62 @@
+{
+    "format" : "tga",
+    "subType" : "TGAv2E",
+    "metadata" : [
+        {
+            "key" : "CreationDate",
+            "value" : "2025-01-14T13:53:32+01:00"
+        },
+        {
+            "key" : "Direction",
+            "value" : "123.7"
+        },
+        {
+            "key" : "Software" ,
+            "value" : "Adobe Photoshop 26.2 (Windows)"
+        },
+        {
+            "key" : "Altitude",
+            "value" : "34"
+        },
+        {
+            "key" : "Author",
+            "value" : "KDE Project"
+        },
+        {
+            "key" : "Copyright",
+            "value" : "@2025 KDE Project"
+        },
+        {
+            "key" : "Description",
+            "value" : "テレビ放送テスト映像。(TV broadcast test image.)"
+        },
+        {
+            "key" : "Latitude",
+            "value" : "44.6478"
+        },
+        {
+            "key" : "LensManufacturer",
+            "value" : "KDE Glasses"
+        },
+        {
+            "key" : "LensModel",
+            "value" : "A1234"
+        },
+        {
+            "key" : "Longitude",
+            "value" : "10.9254"
+        },
+        {
+            "key" : "Manufacturer",
+            "value" : "KFramework"
+        },
+        {
+            "key" : "Model",
+            "value" : "KImageFormats"
+        }
+    ],
+    "resolution" : {
+        "dotsPerMeterX" : 11811,
+        "dotsPerMeterY" : 11812
+    }
+}