use relevant evidence fields for cis_gcp 2.13

[orouz]

Summary of your changes

1. rule evaluation didn't change, just refactored
2. the evidence field returned for the failed case is the list of enabled service usage assets (which assets inventory was not part of), and for the passed case it's the service usage assets indicating assets inventory is enabled
3. assets returned in the evidence field only contain the resource.data fields which are relevant for identification and were used in evaluation

Screenshot/Data

before	after
shows list of full service usage assets as evidence	shows list of assets inventory trimmed service usage assets as evidence

Related Issues

• related https://github.com/elastic/security-team/issues/12315

[mergify]

This pull request does not have a backport label. Could you fix it @orouz? 🙏
To fixup this pull request, you need to add the backport labels for the needed
branches, such as:

• backport-v./d./d./d is the label to automatically backport to the 8./d branch. /d is the digit
• backport-active-all is the label that automatically backports to all active branches.
• backport-active-8 is the label that automatically backports to all active minor branches for the 8 major.
• backport-active-9 is the label that automatically backports to all active minor branches for the 9 major.

[eyalkraft]

Looks good, please test with a failed finding as well (by changing the actual cloud config)