Fix unhandled exceptions, cache unresolvable entities

[rvazarkar]

Description

2 uncaught exceptions were identified in CertAbuseProcessor and LdapPropertyProcessor, this MR addresses them.

Additionally, unresolvable principals were not cached, and where repeatedly looked up which in certain cases could drastically impact performance.

Motivation and Context

https://specterops.atlassian.net/browse/BED-4822
https://specterops.atlassian.net/browse/BED-4836

How Has This Been Tested?

Screenshots (if appropriate):

Types of changes

• Chore (a change that does not modify the application functionality)
• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• Documentation updates are needed, and have been made accordingly.
• I have added and/or updated tests to cover my changes.
• All new and existing tests passed.
• My changes include a database migration.