Router processing fixes

[bengerman13]

This PR does a couple things:

• fix gorouter log processing for platform log instances - this is essentially just copying the app log processing logic
• improve performance for grok on router logs for both platform and app instances. This is done by:
  • anchoring patterns
  • reordering patterns so the patterns corresponding to the most recent CF versions are first
  • changing grok syntax so grok breaks on the first match
• allow app_index to be a - in router logs. We're seeing this in our logs sometimes

This should be a non-breaking change.

[bengerman13]

@Infra-Red any chance we can get this reviewed/merged? We're running this in production and it has fixed parsing and reduced CPU usage massively

[Infra-Red]

Thanks @bengerman13 !