The new math/rand/v2 package includes an m-local global random number
generator that can not be reseeded by the user, which is suitable for
most uses without the RNG pools we have in a number of areas of the code
base.
The new API still does not have an allocation-free way of performing a
seeded operations, due to the long term compiler bug around interface
parameter escapes, and the Source interface.
This change introduces the two APIs that math/rand/v2 can not yet
replace efficiently: seeded Perm() and Shuffle() operations. This
implementation chooses to use the PCG random source from math/rand/v2,
as with sufficient compiler optimization, this source should boil down
to only two on-stack registers for random state under ideal conditions.
Updates #17243
Signed-off-by: James Tucker <james@tailscale.com>
James Tucker