.NET 4.8 Memory Leak

[kenny-sellers]

Description

It was discovered that we are seeing a memory leak in FileOnQ.Imaging.Heif when targeting .NET 4.8. Both the thumbnail (234B) and primary image (234B) are impacted. Below is the benchmarks.

Method	Mean	Error	StdDev	Gen 0	Gen 1	Gen 2	Allocated	Allocated native memory	Native memory leak
Thumbnail_Write	29.09 ms	0.211 ms	0.187 ms	-	-	-	74,504 B	5,125,345 B	234 B
Thumbnail_ToArray	28.79 ms	0.171 ms	0.160 ms	-	-	-	74,504 B	5,124,925 B	234 B
Thumbnail_ToSpan	29.12 ms	0.258 ms	0.215 ms	-	-	-	-	5,124,909 B	234 B
Thumbnail_ToStream	29.11 ms	0.366 ms	0.343 ms	-	-	-	140,816 B	5,124,925 B	234 B

Method	Mean	Error	StdDev	Gen 0	Gen 1	Gen 2	Allocated	Allocated native memory	Native memory leak
PrimaryImage_Write	1.342 s	0.0043 s	0.0038 s	-	-	-	1,951,112 B	222,030,860 B	234 B
PrimaryImage_ToArray	1.343 s	0.0031 s	0.0028 s	-	-	-	1,951,112 B	222,030,552 B	234 B
PrimaryImage_ToSpan	1.342 s	0.0057 s	0.0053 s	-	-	-	-	222,029,928 B	234 B
PrimaryImage_ToStream	1.341 s	0.0043 s	0.0038 s	-	-	-	3,894,032 B	222,030,392 B	234 B

[SkyeHoefling]

Thanks for writing this up @kenny-sellers

This was identified as part of #62