util: introduce kernel utils for pseudorandom number generation

Currently there are two generators. The fast one is the same one the scheduler
is using. The standard one is the same algorithm libroot's rand() uses. Should
there be a need for more cryptographically PRNG MD4 or MD5 might be a good
candidates.
vm: let aslr use kernel utils for random numbers
nfs4: let nfs4 use kernel utils for random numbers
scheduler: let schedulers use kernel utils for random numbers