windows: virtio: add generic shared memory region APIs
windows: virtio: add generic shared memory region APIs

This change allows https://crrev.com/c/3716341 to work on Windows.

BUG=b:240732098
TEST=builds and run the emulator

Change-Id: Ia428350d1323702ddf3cdf5b4105d25429d0857b
Reviewed-on: https://chromium-review.googlesource.com/c/crosvm/crosvm/+/3806338
Commit-Queue: Kaiyi Li <f6fa95ef69f95b15c9d6b9a996e5e7cbcfb76e84@google.com>
Reviewed-by: Richard Otap <42855b52c0c6f03293add2b6c0985b0ba6f15091@google.com>
Auto-Submit: Kaiyi Li <f6fa95ef69f95b15c9d6b9a996e5e7cbcfb76e84@google.com>
Tested-by: Kaiyi Li <f6fa95ef69f95b15c9d6b9a996e5e7cbcfb76e84@google.com>
Reviewed-by: Daniel Verkamp <72bc170b46ec491f7bdd4359a1c0bfed274de40c@chromium.org>
Reviewed-by: Noah Gold <2d4550d8af93bfc6e6fbe1fb1b0cc97a9ee7c3ce@google.com>

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