Add appProtocol to OTLP service ports

[Dragemil]

What this PR does / why we need it:

Adds appProtocol: grpc and appProtocol: http to the OTLP receiver port entries (otlpgrpcport and otlphttpport) in the local-traffic agent service (agent-services.yaml).

Envoy-based service meshes (Istio sidecar/ambient, Gloo, etc.) rely on either port-name prefixes (grpc-, http-) or the appProtocol field to detect application-level protocols. Because otlpgrpcport doesn't match any recognized prefix, the proxy treats the port as plain TCP — breaking gRPC connectivity with:

upstream connect error or disconnect/reset before headers.
reset reason: protocol error

appProtocol is a stable Kubernetes field (GA since v1.20) and is the standard way to declare application-level protocols on service ports.

Which issue this PR fixes

(optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close that issue when PR gets merged)

• fixes #

Special notes for your reviewer:

• This is a non-breaking, additive-only change — appProtocol is ignored by components that don't inspect it.
• Verified that versions 3.154.1 through 3.174.0 do not set appProtocol on these ports.
• No new values.yaml parameters are introduced (the field is unconditionally set when the OTLP receiver is enabled).

Checklist

[Place an '[x]' (no spaces) in all applicable fields. Please remove unrelated fields.]

• All commits are signed (see: signing commits)
• Chart Version semver bump label has been added (use <chartName>/minor-version, <chartName>/patch-version, or <chartName>/no-version-bump)
• For datadog or datadog-operator chart or value changes, update the test baselines (run: make update-test-baselines)

GitHub CI takes care of the below, but are still required:

• Documentation has been updated with helm-docs (run: .github/helm-docs.sh)
• CHANGELOG.md has been updated
• Variables are documented in the README.md