random: always use the PRNG, and use entropy sources to feed it

remove the yarrow module. the hardware modules can push entropy with queue_randomness().
virtio_rng will now push entropy every 300 seconds.
helps with #14937

Change-Id: If76c5deabf61dc616a0e051332f44b89deb6b8a1
Reviewed-on: https://review.haiku-os.org/c/haiku/+/5824
Tested-by: Commit checker robot <no-reply+buildbot@haiku-os.org>
Reviewed-by: waddlesplash <waddlesplash@gmail.com>

Removed 'register' storage class compiler warnings

Change-Id: Iba89a9d0845bf7e816983f903281d33e273f6e35
Reviewed-on: https://review.haiku-os.org/c/haiku/+/5558
Reviewed-by: X512 <danger_mail@list.ru>
Reviewed-by: Adrien Destugues <pulkomandy@pulkomandy.tk>
Tested-by: Commit checker robot <no-reply+buildbot@haiku-os.org>

random: use user_memcpy/user_strlcpy to read/write the user buffer.

* also check the user buffer address.

kernel: Remove possibility to yield to all threads

Kernel support for yielding to all (including lower priority) threads
has been removed. POSIX sched_yield() remains unchanged.

If a thread really needs to yield to everyone it can reduce its priority
to the lowest possible and then yield (it will then need to manually
return to its prvious priority upon continuing).

random: add a Virtio RNG module

* The default module is replaced by the Virtio RNG module when found.
* This can have the undesired effect of rendering /dev/urandom slow.
* Tested with the following QEmu command line option:
-device virtio-rng-pci,rng=rng0 -object rng-random,filename=/dev/random,id=rng0
* moved random.h to private/drivers headers.

random: added a bus interface for RNG modules.

* Yarrow RNG is the default RNG module.

random: move to bus_managers/

kernel: Remove possibility to yield to all threads

Kernel support for yielding to all (including lower priority) threads
has been removed. POSIX sched_yield() remains unchanged.

If a thread really needs to yield to everyone it can reduce its priority
to the lowest possible and then yield (it will then need to manually
return to its prvious priority upon continuing).

random: add a Virtio RNG module

* The default module is replaced by the Virtio RNG module when found.
* This can have the undesired effect of rendering /dev/urandom slow.
* Tested with the following QEmu command line option:
-device virtio-rng-pci,rng=rng0 -object rng-random,filename=/dev/random,id=rng0
* moved random.h to private/drivers headers.

random: added a bus interface for RNG modules.

* Yarrow RNG is the default RNG module.

random: move to bus_managers/