* Optimize policy iterators (go1.23)
This modifies (*Options).GetAllPolicies() to use a go 1.23 iterator
instead of copying all policies on every call, which can be extremely
expensive. All existing usages of this function were updated as
necessary.
Additionally, a new (*Options).NumPolicies() method was added which
quickly computes the number of policies that would be given by
GetAllPolicies(), since there were several usages where only the
number of policies was needed.
* Fix race condition when assigning default envoy opts to a policy
