feat(audience match types): Update condition evaluator for new audience match types

[oakbani]

Summary

This adds support for new audience match type conditions to the condition evaluator:

• exact, exists, gt, lt, and substring conditions
• Abort and return null when appropriate in leaf evaluators
• Null handling in and/or/not evaluators
• Assume implicit "or" when operator is missing

Test Plan

Added new unit tests.
Ran compatibility suite tests for typed audiences

[aliabbasrizvi]

LGTM. Minor feedback.