Support `GatewayPort8080` feature

[mlavacca]

Is there an existing issue for this?

• I have searched the existing issues

Problem Statement

Recently a new extended feature GatewayPort8080 has been introduced upstream, and we need to support it by adding a new listener on port 8080 of Kong.

Proposed Solution

• Add a new listener with port 8080

Acceptance Criteria

• the conformance tests with the feature GatewayPort8080 are run and pass.