Make Anchore gateways configurable

Summary

current istio gateways are hard-coded to Istio-system/main

Steps to reproduce

https://repo1.dso.mil/platform-one/big-bang/apps/security-tools/anchore-enterprise/-/blob/main/chart/templates/bigbang/anchore-vs.yaml#L8-10

https://repo1.dso.mil/platform-one/big-bang/apps/security-tools/anchore-enterprise/-/blob/main/chart/templates/bigbang/anchore-vs.yaml#L30-32

What is the current behavior?

What is the expected behavior?

Configurable gateway

(What you should see instead)

Relevant logs and/or screenshots

(Paste any relevant logs - please use code blocks (```) to format console output, logs, and code as it's very hard to read otherwise.)

Possible fixes

(If you can, link to the line of code that might be responsible for the problem)

/cc {put CODEOWNERs @githandles here}