issues/5253 convert cache-unaligned-requests to per-tenant config

[francoposa]

What this PR does

Moves cache_unaligned_requests into the limits, so that it can be overridden per-tenant.

Allows operators to turn this on for the rare tenants that will actually need it, without ballooning the cache for everyone else in a multi-tenant cell that does not need this.

Global parameter cacheUnalignedRequests was removed from splitAndCacheMiddleware in favor of access to limits helper functions.

Which issue(s) this PR fixes or relates to

Fixes #5253

Checklist

• Tests updated
• Documentation added
• CHANGELOG.md updated - the order of entries should be [CHANGE], [FEATURE], [ENHANCEMENT], [BUGFIX]

[pstibrany]

Thank you. Left comment with one detail to fix, lgtm otherwise.

[pstibrany]

When someone sets this field in their config, we should modify the default limit value.

We should do that in initRuntimeConfig, before calling validation.SetDefaultLimitsForYAMLUnmarshalling, similar to

mimir/pkg/mimir/modules.go

Lines 273 to 279 in 52d9875

	// QueryIngestersWithin is moving from a global config that can in the querier yaml to a limit config
	// We need to preserve the option in the querier yaml for two releases
	// If the querier config is configured by the user, the default limit is overwritten
	// TODO: Remove in Mimir 2.11.0
	if t.Cfg.Querier.QueryIngestersWithin != querier.DefaultQuerierCfgQueryIngestersWithin {
	t.Cfg.LimitsConfig.QueryIngestersWithin = model.Duration(t.Cfg.Querier.QueryIngestersWithin)
	}

[francoposa]

this is addressed now;

Is there a good place in the docs to put a little playbook for migrating a config option into the limits section?

There are quite a few checklist items for this process, and I would expect this is far from the last time it will be done.

[pstibrany]

Is there a good place in the docs to put a little playbook for migrating a config option into the limits section?

That's a great idea. We can create short document in docs/internal/contributing directory.

[pstibrany]

Thank you!