arrow

ARROW-10719: [C#] ArrowStreamWriter doesn't write schema metadata

Add support for reading and writing Schema and Field metadata

Also, reducing some allocations in a few spots.

Tagging people who have contributed to the C# library in the past year for review. (Feel free to ignore if you don't have time.)

@pgovind @suhsteve @chutchinson @Ulimo @mr-smidge @zgramana @HashidaTKS @nhustler

cc @olgacarpenter

Closes #8902 from eerhardt/Metadata

Authored-by: Eric Erhardt <eric.erhardt@microsoft.com>
Signed-off-by: Eric Erhardt <eric.erhardt@microsoft.com>