Support SYSLOG_IDENTIFIER for systemd filter in the otelcol config

[dindurthy]

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We have calico installed in our clusters. Network policies that log traffic correspond to kernel logs, .e.g SYSLOG_IDENTIFIER=kernel. Previously, we were able to do this with the fluent-bit config:

fluent-bit:
  config:
    inputs: |
      [INPUT]
          Name            systemd
          Systemd_Filter  SYSLOG_IDENTIFIER=kernel

There doesn't appear to be a way to do this with otelcol

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Otelcol config options to filter logs based on SYSLOG_IDENTIFIER exposed via helm value inputs

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[dindurthy]

Previously brought up on a tangential issue