Update quay.io/solo-io/gloo-mesh-envoy Docker tag to v2.3.12

This MR contains the following updates:

Package	Type	Update	Change
quay.io/solo-io/gloo-mesh-envoy	ironbank-docker	patch	2.3.11 -> 2.3.12
quay.io/solo-io/gloo-mesh-envoy		patch	2.3.11 -> 2.3.12
quay.io/solo-io/gloo-mesh-envoy	stage	patch	2.3.11 -> 2.3.12

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