feat(operator)!: Add configuration option for dropping OTLP attributes

[xperimental]

What this PR does / why we need it:

The Loki Operator already supports configuring whether to store OTLP attributes as stream labels or structured metadata, but the option to drop attributes was omitted from the LokiStack API, because of a misunderstanding that "drop" is the default behavior (the actual default behavior is "structured metadata".

This PR adds the drop capability to the LokiStack API as well.

Which issue(s) this PR fixes:

Fixes LOG-6507.

Special notes for your reviewer:

• If "structured metadata" is the default behavior, I wonder if we should remove the StructuredMetadata attribute of the LokiStack (instead of just deprecating it). I think it's still a source of confusion for the user and removing it would also reduce the code needed in the operator quite a bit (mostly validation). This would be a breaking change though.
  • We have decided to include the breaking change. I'll do a bit more testing tomorrow and will take the PR out of draft then.

Checklist

• Reviewed the CONTRIBUTING.md guide (required)
• Documentation added (Loki Operator website will be updated in a separate PR)
• Tests updated
• Title matches the required conventional commits format, see here

[JoaoBraveCoding]

Still have to test but overall lgtm. Good job 🙌

Small nit comment regarding the use of errList = append(errList, ...). Sometimes we use this with just an error where other times with a function call. Although this makes the code more compact I feel that sometimes it makes it a bit harder to follow. Maybe moving instances with function calls to an if and only appending to errList if the result yields a list of errors. This is just a suggestion feel free to ignore if you feel it will not improve the code maintenance.