rand: move rand_{unix,vms,vxworks,win}.c without change to preserve history

Reviewed-by: Paul Dale <paul.dale@oracle.com>
(Merged from https://github.com/openssl/openssl/pull/11682)

diff --git a/crypto/rand/rand_unix.c b/providers/implementations/rands/seeding/rand_unix.c
similarity index 100%
rename from crypto/rand/rand_unix.c
rename to providers/implementations/rands/seeding/rand_unix.c

diff --git a/crypto/rand/rand_vms.c b/providers/implementations/rands/seeding/rand_vms.c
similarity index 100%
rename from crypto/rand/rand_vms.c
rename to providers/implementations/rands/seeding/rand_vms.c

diff --git a/crypto/rand/rand_vxworks.c b/providers/implementations/rands/seeding/rand_vxworks.c
similarity index 100%
rename from crypto/rand/rand_vxworks.c
rename to providers/implementations/rands/seeding/rand_vxworks.c

diff --git a/crypto/rand/rand_win.c b/providers/implementations/rands/seeding/rand_win.c
similarity index 100%
rename from crypto/rand/rand_win.c
rename to providers/implementations/rands/seeding/rand_win.c