dnsdist: allow skipping arbitrary EDNS options when computing packet hash

[chbruyand]

Short description

This adds a new option to newPacketCache() to skip arbitrary EDNS options when hashing packets.
I was a bit unsure to keep the cookieHashing setting but this makes the lua configuration more readable.

It also affects recursor's packet cache so must be reviewed carrefully.

Fix #10585

Checklist

I have:

• read the CONTRIBUTING.md document
• compiled this code
• tested this code
• included documentation (including possible behaviour changes)
• documented the code
• added or modified regression test(s)
• added or modified unit test(s)

[rgacogne]

Two small nits that would not prevent the merge of this PR anyway. Great work, thanks!