Commit Message: fix potential null dereference in ext_authz
Additional Description:

Previously, if ext_authz had emit filter state stats set to true and another filter added filter state under the ext authz filter's name, it would result in a null dereference. The member logging_info_ would not be set in initiateCall after seeing there was already data there. Later, we would dereference logging_info_ to update the stats as if it were initialized already.

I've added a check for a null logging_info_ and added logging & a stat for when there's a filter state naming collision.

I also made some readability improvements to the ext_authz test.

Risk Level: low
Testing: unit tested
Docs Changes: none
Release Notes: none
Platform Specific Features: none

Request variables

Key	Value
ref	2eac096
sha	8b0a04b
pr	36268
base-sha	d5834c1
actor	@antoniovleonti
message	fix potential null dereference in ext_authz...
started	1728928129.766703
target-branch	main
trusted	false

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