Fix Fail2Ban and Allow2Ban not banning with dalli 4 and 5

[santib]

Problem

With dalli 4 and 5, Fail2Ban and Allow2Ban never ban when the store is a Dalli::Client (directly or through a ConnectionPool).

Fail2Ban#ban! writes the Integer 1, and DalliProxy#write passes it to client.set(..., raw: true). Dalli 3 converted it with to_s; dalli 4 and 5 raise instead:

Dalli raw mode requires string values, got: Integer (Dalli::MarshalError)

DalliProxy rescues Dalli::DalliError and returns nil, so the ban key is never written and banned? is always false. Throttling is not affected because it uses memcached's incr, which does not go through the serializer.

Fix

Call value.to_s before the raw set in DalliProxy#write. Same behavior as dalli 3 did internally.

Verification

Adds dalli 4 and dalli 5 to the CI matrix (appraisals and gemfiles, excluding the Ruby versions each one does not support: dalli 4 requires Ruby >= 3.1, dalli 5 requires Ruby >= 3.3). Without the fix, works for fail2ban and works for allow2ban in spec/acceptance/stores/dalli_client_spec.rb fail on every dalli 4/5 job (expected 403, got 200).