Add support for creating serial devices using the `crosvm devices`
command.
BUG=b:217480043
TEST=`crosvm devices --serial hardware=virtio-console,console,stdin,type=stdout,earlycon,vhost=/tmp/vu-serial`
results in a working vhost-user serial device.
TEST=`crosvm devices --serial hardware=virtio-console,console,stdin,type=stdout,earlycon,vhost=0000:00:10.0`
results in a working VVU serial device.
Change-Id: I06fa4c8e27e90fa00c64b38dd25c7e9a91ee77fc
Reviewed-on: https://chromium-review.googlesource.com/c/crosvm/crosvm/+/3762975
Reviewed-by: Morg <morg@chromium.org>
Commit-Queue: Alexandre Courbot <acourbot@chromium.org>
Tested-by: Alexandre Courbot <acourbot@chromium.org>
Reviewed-by: Keiichi Watanabe <keiichiw@chromium.org>
