Allow large byte arrays in received messages to be allocated from ArrayPool

[bill-poole]

I have a gRPC service that streams data from clients in a request stream, where each message is a chunk of data up to 1 MB. Currently, the gRPC library allocates a new array for each chunk, creating a lot of GC pressure, especially because the arrays are all allocated on the LOH. It would be great if we could configure the gRPC endpoint in ASP.NET to allocate those arrays from ArrayPool<byte>.Shared, rather than allocating new arrays. My endpoint logic would then be responsible for returning those arrays to the array pool when processing is complete.