EXIF improvements and bugfixes

- Fixes a writing issue for float values ​​less than 1
- Fixes a missing definition of `EXIF_DATETIMEDIGITIZED` tag
- Adds support for some common camera shot metadata
- Adds missing metadata to writing tests

The following plugins automatically gain support for the new metadata: AVIF, IFF, HEIF, JXL, JXR, PSD and TGA (V2E).

The new metadata added with this patch is usually saved by smartphones (e.g. iPhone or Google Pixel).

autotests/write/basic/jxr.json

@@ -41,6 +41,10 @@
             "key" : "LensModel",
             "value" : "A1234"
         },
+        {
+            "key" : "LensSerialNumber",
+            "value" : "S/N:1234567"
+        },
         {
             "key" : "Longitude",
             "value" : "10.9254"
@@ -52,6 +56,50 @@
         {
             "key" : "Model",
             "value" : "KImageFormats"
+        },
+        {
+            "key" : "SerialNumber",
+            "value" : "S/N:7654321"
+        },
+        {
+            "key" : "Speed",
+            "value" : "13.2"
+        },
+        {
+            "key" : "DigitalZoomRatio",
+            "value" : "3.4"
+        },
+        {
+            "key" : "ExposureMode",
+            "value" : "2"
+        },
+        {
+            "key" : "ExposureProgram",
+            "value" : "6"
+        },
+        {
+            "key" : "ExposureTime",
+            "value" : "0.004"
+        },
+        {
+            "key" : "Flash",
+            "value" : "16"
+        },
+        {
+            "key" : "FNumber",
+            "value" : "1.6"
+        },
+        {
+            "key" : "FocalLength",
+            "value" : "5.96"
+        },
+        {
+            "key" : "ISOSpeedRatings",
+            "value" : "50"
+        },
+        {
+            "key" : "WhiteBalance",
+            "value" : "1"
         }
     ],
     "resolution" : {