Support zstd compression

[bgrainger]

MySQL 8.0.18 introduces the option to use zstd compression:

https://dev.mysql.com/doc/relnotes/mysql/8.0/en/news-8-0-18.html#mysqld-8-0-18-connection-control

MySQL now provides more control over the use of compression to minimize the number of bytes sent over connections to the server. Previously, a given connection was either uncompressed or used the zlib compression algorithm. Now, it is also possible to use the zstd algorithm (zstd 1.3), and to select a compression level for zstd connections.

See also WL12039 and WL12475.

There are a few NuGet packages for zstandard; at a glance they appear to be wrappers over the native library, not a managed implementation.

This should probably be implemented as an optional plugin that can be enabled at runtime, rather than adding more code and dependencies to the core package.

[bgrainger]

This should be much easier to deliver if Zstandard comes to .NET 7.0: https://github.com/dotnet/runtime/issues/59591

[bgrainger]

MySql.Data 8.0.33 removed zstd support (https://dev.mysql.com/doc/relnotes/connector-net/en/news-8-0-33.html):

The zstd compression algorithm is deactivated in the connector. (Bug #35281610)

[rykr]

That was temporary. It's coming back in the next version

[bgrainger]

I missed that a 100% C# port of Zstandard has been created: https://github.com/oleg-st/ZstdSharp