Release 6.0.6

There were some nontrivial conflicts to resolve, NEWS + the line
    ctx->vld_limit_crypto = KR_VLD_LIMIT_CRYPTO_DEFAULT;
(I had this resolution prepared for a long time.)

DNSSEC verification complexity could be exploited to exhaust CPU resources and stall DNS resolvers.

Solution boils down mainly to limiting crypto-validations per packet.

in a separate commit, as it will tend to conflict if patching

Improve: don't retry in this case.

Keep the first error in case priorities are equal.

At least with the current KeyTrap topic that should work better,
but blaming a single error is alchemy anyway, at least in some cases.

The value is in IANA registry, so it's very constant anyway.

That's when searching NSEC3 aggressive cache.

Limit combination of iterations and salt length, based on estimated
expense of the computation.  Note that the result only differs for
salt length > 44 which is rather nonsensical and very rare:
https://chat.dns-oarc.net/community/pl/h58qx9sjkbgt9dajb7x988p78a

Also done by BIND9 >= 9.19.19:
https://gitlab.isc.org/isc-projects/bind9/-/merge_requests/8515

The latest real-life measurements show that values above 50 are rare:
https://chat.dns-oarc.net/community/pl/aadp9wwrp7g7ux1b8chbzebmze