enable default collector

[aphralG]

Proposed changes

If valid command server block is configured in the nginx-agent.conf but no processors are found in the collector block, a collector will be created using defaults.

• The host and auth from the command server will be used in the collector (More detail on Defaults Below)
• If command server is missing any settings (auth, tls etc) the default collector is not created
• Removed collector from pre-install and upgrade-agent-config script

Default Collector Settings

• Receiver - Host Metric enabled
  • CPU, Disk, Network, Filesystem, Memory Scrapers Enabled
  • Collection Interval set to 1 min
  • InitialDelay set to 1 second
• Exporters - OtlpExporters enbaled
  • Server set to Command Server configuration
  • TLS set to Command TLS configuration
  • Authenticator set to "headers_setter",
• Extensions - HeadersSetter enabled
  • Action set to "insert"
  • Key set to "authorization"
  • Value set to Command Auth Token

Checklist

Before creating a PR, run through this checklist and mark each as complete.

• I have read the CONTRIBUTING document
• I have run make install-tools and have attached any dependency changes to this pull request
• If applicable, I have added tests that prove my fix is effective or that my feature works
• If applicable, I have checked that any relevant tests pass after adding my changes
• If applicable, I have updated any relevant documentation (README.md)
• If applicable, I have tested my cross-platform changes on Ubuntu 22, Redhat 8, SUSE 15 and FreeBSD 13