HSH: Limit the number of non matching variants evaluated against the ban list during lookup

[walid-git]

This is an implementation of the solution suggested by @bsdphk in #4236 (comment)

It adds a parameter to limit the number of possibly non matching variants that we evaluate against the ban list during a lookup.

Leaving this as a draft until we agree on the parameter name.

Refs: #4236

[nigoroll]

after bugwash discussion:

• we settled on ban_any_variant for the name
• the default should be changed to 0 with a major release (added a reminder to 8.0 release checklist #3352)
• the parameter should be copied to a local variable for consistency, otherwise both ban_checks related conditions or none could become true

[walid-git]

• we settled on ban_any_variant for the name
• the default should be changed to 0 with a major release (added a reminder to 8.0 release checklist #3352)
• the parameter should be copied to a local variable for consistency, otherwise both ban_checks related conditions or none could become true

Also added a paragraph in purging.rst about the new ban_any_variant parameter.

[walid-git]

bugwash: make docs clearer

[walid-git]

Added 744e840. @bsdphk let me know if this is clearer now.

[nigoroll]

I was not addressed, but I think the document improvement is very good.