Provide a way to adjust the initial window size that does not also disable BDP estimation

There are at least a couple options here:

1. Change the existing Dial/ServerOptions ([e.g.](https://pkg.go.dev/google.golang.org/grpc#WithInitialConnWindowSize)) so they do not disabled BDP estimation
  - Optionally, add another set of options that does disable BDP estimation.
2. Add new Dial/ServerOptions to set the size like the existing ones, but which do not also disable BDP esimation.
