Updating INCREX command arg - SATURATE now controls overflow behaviour

[petyaslavova]

Description of change

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Note

Medium Risk
Public API change on increx (breaking for overflow= callers) and different error vs return behavior on bound violations; otherwise test and CI wiring.

Overview
increx is aligned with the updated Redis command: the overflow string option (FAIL / REJECT / SAT) is replaced by a boolean saturate that emits the SATURATE wire flag when true. Docs and validation for invalid overflow values are removed accordingly.

Default out-of-bounds behavior no longer raises ResponseError on the client; rejected increments return [current_value, 0] and leave the key (and TTL) unchanged. Tests were renamed/extended for that semantics, including integer type-limit cases with saturate=True on the sync path.

CI runs Redis 8.8 against a custom Debian image instead of 8.8-rc1. Async pub/sub test_late_subscribe calls connect() before run() to avoid a CI race instead of polling for connection readiness.

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✅ No security findings were detected in this PR

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