fix(envoy-filter): properly removes headers

[bartoszmajsak]

Description

The current implementation incorrectly calls removal of a header which is manifested in ingress gateway proxy logs when trying to access inference service:

envoy lua external/envoy/source/extensions/filters/http/lua/lua_filter.cc:930  script log: [string "function envoy_on_request(request_handle)..."]:10: bad argument #1 to 'remove' (N5Envoy10Extensions11HttpFilters3Lua16HeaderMapWrapperE expected, got string`

This fixes the Lua syntax and marks Service Mesh Features related to KServe setup as Managed(). This ensures that updating the existing filters will happen on operator upgrade or next reconcile.

How Has This Been Tested?

• deploy latest incubation operator
• create DSCI with Service Mesh enabled
• create DSC with KServe enabled
• check the content of the filter oc get envoyfilter/envoy-oauth-temp-fix-after -n istio-system -o yaml. Notice wrong syntax .remove in Lua snippet
• try accessing ISVC and notice error in the ingress gateway logs
• deploy operator image based on this PR
• confirm logs are not showing up on the ingress gateway proxy
• check the content of the filter oc get envoyfilter/envoy-oauth-temp-fix-after -n istio-system -o yaml. Notice correct/patched syntax :remove in Lua snippet

Screenshot or short clip

Merge criteria

• [x] You have read the contributors guide.
• [x] Commit messages are meaningful - have a clear and concise summary and detailed explanation of what was changed and why.
• [x] Pull Request contains a description of the solution, a link to the JIRA issue, and to any dependent or related Pull Request.
• [x] Testing instructions have been added in the PR body (for PRs involving changes that are not immediately obvious).
• [x] The developer has manually tested the changes and verified that the changes work

[openshift-ci[bot]]

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