feat: dynamically set bundled otelcol host through the Connect gcfg

[mconflitti-pbc]

NOTE: Include these changes in the Connect 2026.03.0 Helm chart release PR. Can target this PR to that branch prior to merging that one to main.

Summary

When config.OpenTelemetry.Enabled is set to true, automatically defaults CollectorAdvertiseHost to the Connect service's cluster-internal DNS name (<fullname>.<namespace>.svc.cluster.local). Users can override this via config.OpenTelemetry.CollectorAdvertiseHost. No [OpenTelemetry] section is rendered when disabled.

Manual checks

# No [OpenTelemetry] section when disabled (default)
$ helm template my-release ./charts/rstudio-connect --set sharedStorage.create=true --set launcher.enabled=false | grep -A 5 OpenTelemetry
(no output)

# CollectorHost defaults to service DNS when enabled
$ helm template my-release ./charts/rstudio-connect --set sharedStorage.create=true --set launcher.enabled=false --set config.OpenTelemetry.Enabled=true | grep -A 5 OpenTelemetry
    [OpenTelemetry]
    CollectorAdvertiseHost = my-release-rstudio-connect.rsc-dev.svc.cluster.local
    Enabled = true

    [Python]
    Enabled = true

# User override takes precedence
$ helm template my-release ./charts/rstudio-connect --set sharedStorage.create=true --set launcher.enabled=false --set config.OpenTelemetry.Enabled=true --set config.OpenTelemetry.CollectorAdvertiseHost=customer.example.com | grep -A 5 OpenTelemetry
    [OpenTelemetry]
    CollectorAdvertiseHost = customer.example.com
    Enabled = true

    [Python]
    Enabled = true

[dbkegley]

The template changes look right to me. We'll also need to bump the chart version and add news. Make sure to run just docs after modifying the chart.yaml.