[DOCS] Add DSL Filters to Event Correlation (EQL) rule creation

[joepeeples]

Description

PR elastic/kibana#132507 adds filters to event correlations within the Security Detection rules.

From issue elastic/kibana#101047:

Describe the feature: Add filters to event correlations within the Security Detection rules, this is possible inside EQL but does not seem to be supported inside Detections.

Describe a specific use case for the feature: If I need to search for the same values across multiple documents, with only a couple of those fields changing each time but more than one field across the documents staying the same, the EQL is less efficient than the DSL is.

Notes

• Filters are applied to both rule preview (while creating rule) and during actual rule execution.

[joepeeples]

Reassigning to @jmikell821 since she's documenting rule creation for 8.4 in #2258.