Use larger read buffers for virtio-console.
Use larger read buffers for virtio-console.

This improves performance on high-throughput virtio-console
communication.

Test: Run together with https://android-review.googlesource.com/c/device/google/cuttlefish/+/1459363
Bug: b/155695742
Change-Id: I78062f648ee18040c80ace109ab4d62e8ee1fbca
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crosvm/+/2470376
Reviewed-by: Daniel Verkamp <72bc170b46ec491f7bdd4359a1c0bfed274de40c@chromium.org>
Tested-by: Daniel Verkamp <72bc170b46ec491f7bdd4359a1c0bfed274de40c@chromium.org>
Tested-by: kokoro <2ac7b1f3fa578934c95181d4272be0d3bca00121@google.com>
Commit-Queue: Cody Schuffelen <7618f12f8c1ef40a3c8bf8909fc72185c1ec8ce8@google.com>

google/crosvm,google/crosvm,google/crosvm,google/crosvm