[Security Solution] [PRC Milestone 3] Update KQL filters and convertRulesFilterToKQL method to rely on new Prebuilt schema

[jpdjere]

Prebuilt Rule Customization Epic - Milestone 3: #174168
Main Epic: https://github.com/elastic/security-team/issues/1974 (internal)

Additional Material:
- Milestone 3 - Software Design RFC
- Prebuilt Rules Customization Technical Design

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Description:

Across our application, both in the frontend and serverside, we use KQL filters to retrieve rules based on whether they are prebuilt rules or not - this means that the current behaviour of these values relies on the immutable field being set to either true or false.

With the introduction of the new prebuilt field, we will want to rely on this new field to determine if a rule is prebuilt during retrieval of rules.

At the same time, we need to maintain backwards compatibility: in order to determine if a rule is prebuilt, preferentially search for the existence of the prebuilt field; if that doesn't exist, fallback to the legacy logic of checking a rule's immutable value.

This means that we will need to update the constants and KQL filters that we have hardcoded in our application, as well as the convertRulesFilterToKQL method, to reflect the new schema.

The updates needed are described in the KQL filters and the convertRulesFilterToKQL method section of the RFC.

[elasticmachine]

Pinging @elastic/security-detection-rule-management (Team:Detection Rule Management)

[elasticmachine]

Pinging @elastic/security-detections-response (Team:Detections and Resp)

[elasticmachine]

Pinging @elastic/security-solution (Team: SecuritySolution)

[jpdjere]

Closing in favour of new tickets planned: #174168 (comment)