Setup check to warn if Redis is used as local cache

[ChristophWurst]

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Is your feature request related to a problem? Please describe.

1. Redis is known to cause issues for local cache
2. Redis is slower than APCu <- loading the /apps/dashboard route. That is for Redis on the same host. In a real cluster the difference will be a lot bigger.

https://docs.nextcloud.com/server/latest/admin_manual/configuration_server/caching_configuration.html#redis-configuration-in-nextcloud-config-php

Describe the solution you'd like

Add a setup check that warns if memcache.local===Redis

Describe alternatives you've considered

N/a

Additional context

N/a

[solracsf]

Redis is known to cause issues for local cache

Are these documented? We're using it since v18 without any (noticeable) issue. 🤔

[ChristophWurst]

https://docs.nextcloud.com/server/latest/admin_manual/configuration_server/caching_configuration.html#redis-configuration-in-nextcloud-config-php

Using Redis for local cache on a multi-server setup can cause issues. Also, even on a single-server setup, APCu (see section above) should be faster.