Rework of #30781 which was reverted in #31017 due to ASAN fuzzer issues

The ASAN fuzzer issues are unrelated to the net-new code here and will affect any code that calls CEL Parse.

The main differences between this and the original PR:

• Refactored out expression/mathching code into separate util classes
• Preserve the expr object from which ParsedExpr are built per #30781 (comment)
• Conditionally fuzz the request_attributes and response_attributes fields on non-ASAN fuzzing due to unrelated issue with ASAN fuzzing in CEL parsing per #31017 (comment)

Commit Message:
Introduce the ability to send attributes in the External Processing Request
Additional Description:
Risk Level: Low
Testing: Integration tests for request/response attributes

Release Notes: N/A
Platform Specific Features: CEL parsing will not work on Windows

Request variables

Key	Value
ref	9ff7b63f72b87794a9c770876bde9845cf232620
sha	cfe7006
pr	31090
base-sha	f20b6ca
actor	@jbohanon
message	ext_proc: send attributes...
started	1705612277.299341
target-branch	main
trusted	false

Container image/s (as used in this CI run)

Envoy version (as used in this CI run)