observIQ exporter - various touchups

[BinaryFissionGames]

Description:
Contains a few small changes to the observiqexporter:

• Adds support for the secret_key configuration option;
  • This may be used instead of the API key; Only one of the two (API key or secret key) may be used to authenticate.
• Updated severity mappings between otel severities and observIQ severities
• Added headers that identify the agent for the http request to ingest logs
• Implemented feedback that was left on observIQ exporter - Conversion to observIQ format implementation #4113

Link to tracking Issue: N/A

Testing:

• Added test to ensure secret key/api key headers are set based on configuration
• Added test to ensure that both secret key and api key may not be set

Documentation:

• Documented new secret_key parameter