LibVideo: Implement VP9 intra-predicted frame decoding

The first keyframe of the test video can be decoded with these changes.

Raw memory allocations in the Parser have been replaced with Vector or
Array to avoid memory leaks and OOBs.

Userland/Libraries/LibVideo/DecoderError.h

@@ -22,6 +22,7 @@ using DecoderErrorOr = ErrorOr<T, DecoderError>;
 enum class DecoderErrorCategory : u32 {
     Unknown,
     IO,
+    Memory,
     // The input is corrupted.
     Corrupted,
     // The input uses features that are not yet implemented.
@@ -79,4 +80,6 @@ private:
         _result.release_value();                                           \
     })
 
+#define DECODER_TRY_ALLOC(expression) DECODER_TRY(DecoderErrorCategory::Memory, expression)
+
 }