HTTP/2: Consider increasing default window sizes

[JamesNK]

Is there an existing issue for this?

• I have searched the existing issues

Is your feature request related to a problem? Please describe the problem.

The default HTTP/2 window sizes in Kestrel are relatively small. 96 KB for stream window size, 128 KB for connection window size. These will limit the speed a client can upload to Kestrel, especially in a high-latency scenario.

This is a simpler alternative to dynamic window sizing.

Describe the solution you'd like

Increasing window size is simple to do. Should think about the implications of larger sizes from perf and resource usage, and consider making them bigger.

Additional context

No response

[adityamandaleeka]

Notes: we can introduce artificial latency in our benchmarks to tune the right values here.