Batch large pipelined Redis commands

What does this MR do and why?

This MR breaks large pipelines in Gitlab::Redis::Cache into batches of 1000.

It uses the same idea as reactive_set_cache's keys.each_slice(1000) { |subset| pipeline.unlink(*subset) }. In Redis, pipelines sizes should be capped since the server holds the responses in memory and huge pipelines could place an unexpectedly large load on the server as seen in the incident issue below.

See https://gitlab.com/gitlab-com/gl-infra/reliability/-/issues/23699. This is CA for gitlab-com/gl-infra/production#14406 (closed).

Does not affect self-managed as it is behind a feature-flag.

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