Helm: Enabled usage of network connection for custom discovery handler.

[karok2m]

What this PR does / why we need it:

This PR adds ability to use networked connection for connecting to custom discovery handler from AKRI agent.

The PR introduces 2 parameters in deployment\helm\values.yaml file of the Helm chart:

custom:
  ...
  # discovery defines a set of values for a custom discovery handler DaemonSet
  discovery:
    ...
    # useNetworkConnection specifies whether the discovery handler should make a networked connection
    # with Agents, using its pod IP address when registering
    useNetworkConnection: false
    # port specifies (when useNetworkConnection is true) the port on which the discovery handler advertises its discovery service
    port: 10000

Then those parameters are processed in deployment\helm\templates\custom-discovery-handler.yaml to expose the specified port and add POD_IP environment variable that can be used by the discovery handler to register itself with AKRI agent.

This aligns configuration of custom discovery handler with the others which already have useNetworkConnection and port parameters.

Special notes for your reviewer:

The changes are only on the Helm chart side. No changes were added to the Rust code, so cargo-related checkboxes below are irrelevant.

If applicable:

• this PR has an associated PR with documentation in akri-docs
• this PR contains unit tests
• added code adheres to standard Rust formatting (cargo fmt)
• code builds properly (cargo build)
• code is free of common mistakes (cargo clippy)
• all Akri tests succeed (cargo test)
• inline documentation builds (cargo doc)
• all commits pass the DCO bot check by being signed off -- see the failing DCO check for instructions on how to retroactively sign commits

[kate-goldenring]

/version patch

[kate-goldenring]

@karok2m sorry for the delay on this! Thank you for getting our custom templates up to speed with our other protocols.