ToSpan Allocates Extra Bytes in .NET 5 and .NET 6

[SkyeHoefling]

Description

In both .NET 5 and .NET 6 benchmarks the ToSpan has extra allocations that don't make sense. This API wraps the native pointer from the encoders project and it shouldn't be creating any additional allocations. See benchmark table below.

The benchmarks have been ran on different machines the important value is the memory allocation

Method	Mean	Error	StdDev	Allocated native memory	Native memory leak	Allocated
Thumbnail_ToSpan (NET 5)	58.68 ms	1.150 ms	1.889 ms	5,123,597 B	-	120 B
PrimaryImage_ToSpan (NET 5)	2.981 s	0.0252 s	0.0236 s	222,028,216 B	-	88 B
Thumbnail_ToSpan (NET 6)	47.54 ms	0.425 ms	0.398 ms	5,123,853 B	-	600 B
PrimaryImage_ToSpan (NET 6)	2.968 s	0.0271 s	0.0241 s	222,029,080 B	-	616 B