Support for Split output Logging

[ben-taussig-solo]

Description

• Resolves https://github.com/solo-io/gloo/issues/4833
• When the SPLIT_LOG_OUTPUT environment variable is specified, a global logger is created with the following characteristics:
  • debug/info/warning are written to stdout
  • error/fatal/panic are written to stderr
  • Configuration is otherwise identical to the default logger
• When SPLIT_LOG_OUTPUT is unspecified, logging configuration is unchanged

[solo-changelog-bot[bot]]

Issues linked to changelog: https://github.com/solo-io/gloo/issues/5048