feat: Add step param to Patterns Query API

[benclive]

What this PR does / why we need it:

• Adds an optional step parameter to the Patterns Query API
• This returns Pattern counts aggregated by the step duration instead of the raw samples we currently store.
  • Patterns continue to be stored in 10 second samples in the backend as this PR this only affects the read path.

Which issue(s) this PR fixes:
Fixes #12689

Special notes for your reviewer:

• There may be some aggregation code elsewhere in Loki that can be re-used here.
• Step is currently unused by the frontend but will default to a minimum of 10 seconds (the sample resolution) if not specified.

Checklist

• Reviewed the CONTRIBUTING.md guide (required)
• Documentation added
• Tests updated
• Title matches the required conventional commits format, see here
• Changes that require user attention or interaction to upgrade are documented in docs/sources/setup/upgrade/_index.md
• For Helm chart changes bump the Helm chart version in production/helm/loki/Chart.yaml and update production/helm/loki/CHANGELOG.md and production/helm/loki/README.md. Example PR
• If the change is deprecating or removing a configuration option, update the deprecated-config.yaml and deleted-config.yaml files respectively in the tools/deprecated-config-checker directory. Example PR

[benclive]

The stepping functionality shunts values into the step bucket before the sample TS, so these tests all had to be skewed down by to an even numbered millisecond as the step size is 2ms. Let me know if you don't agree with this behaviour.

[cyriltovena]

Sounds good, but you could have made the step configurable in the tests and default to previous behaviour.

[cyriltovena]

I think there updates requires in those files too.

https://github.com/grafana/loki/blob/main/pkg/loghttp/patterns.go#L9
https://github.com/grafana/loki/blob/main/pkg/querier/queryrange/codec.go#L999

The frontend in distributed mode is a huge minefields, I suggest you give a go and test it in dev to make sure it works correctly. Hit me up if you need help for doing so.

[cyriltovena]

Lgtm

The http parsing could use some tests but nothing blocking