I would like System.Text.Json to serialize/deserialize Memory/ReadOnlyMemory<T> using the same logic as it uses for T[].

This implies:

• Memory<byte> should be base64-encoded just like byte[] is
• Memory<FooBar> should be serialized as appropriate for the type FooBar, same as FooBar[] would.

The main motivation is that I have an array from ArrayPool<T>.Shared, which can have space for more items than I actually need. To serialize only a segment of the array, I would like to use Memory<T> to identify only use "used" part of the array.