Helm chart of openobserve-collector 0.4.0 breaks the default config

[llc1123]

In #168, the exporters defined in pipelines are removed. But the instructions of deploying the collector both in o2 data sources panel and the README of the chart repo lacks the additional required values.

The following values need to be added if using the latest chart:

# Previously only the following are needed
exporters:
  otlphttp/openobserve:
    endpoint: http://o2-openobserve-router.openobserve.svc.cluster.local:5080/api/default
    headers:
      Authorization: Basic <token>
  otlphttp/openobserve_k8s_events:
    endpoint: http://o2-openobserve-router.openobserve.svc.cluster.local:5080/api/default
    headers:
      Authorization: Basic <token>
      stream-name: k8s_events # This line also needs to be added

# Newly required
agent:
  service:
    pipelines:
      logs:
        exporters:
          - otlphttp/openobserve
      metrics:
        exporters:
          - otlphttp/openobserve

gateway:
  service:
    pipelines:
      logs/k8s_events:
        exporters:
          - otlphttp/openobserve_k8s_events
      logs/k8s_pods:
        exporters:
          - otlphttp/openobserve
      metrics:
        exporters:
          - otlphttp/openobserve
      traces:
        exporters:
          - otlphttp/openobserve
          - servicegraph