fix: enable default config v2 for oxia charts

[mattisonchao]

Motivation

• Oxia-backed Pulsar clusters need the operator's default config v2 profile enabled on PulsarBroker, BookKeeperCluster, and PulsarProxy resources.
• The operator does not enable DEFAULT_CONFIG_V2 by default, so the charts need to opt Oxia installs into the profile explicitly.

Modifications

• Add cloud.streamnative.io/config-profile: default-config-v2 to sn-platform and sn-platform-slim broker, bookkeeper, and proxy CR templates when pulsar_metadata.provider is oxia.
• Preserve explicit user-provided cloud.streamnative.io/config-profile annotations so custom profiles are not overwritten.
• Leave non-Oxia metadata installs unchanged.

Testing

• git diff --check origin/master...HEAD
• helm lint ./charts/sn-platform-slim -f examples/sn-platform/values-oxia.yaml
• helm lint ./charts/sn-platform -f examples/sn-platform/values-oxia.yaml
• helm template render checks for Oxia, default metadata, and explicit config-profile override cases on both charts
• Applied the sn-platform-slim chart to a local kind cluster and verified PulsarBroker, BookKeeperCluster, and PulsarProxy CR annotations plus broker healthcheck

[github-actions]

@mattisonchao:Thanks for your contribution. For this PR, do we need to update docs?
(The PR template contains info about doc, which helps others know more about the changes. Can you provide doc-related info in this and future PR descriptions? Thanks)