PLT-951 Add PHP 8 support

[mrliptontea]

• PLT-951
• Add PHP 8 support
• Require ext-mongodb >= 1.7.0
  • Enforce that $readPreference is a string
  • Switch from ReadPreference->getMode() to getModeString()
• Require psr/log instead of Monolog
  • Monolog is now a dev-only package
• Add Resque compatibility layer
  • Allow library to work against current latest release but also development which includes namespace changes and also requires that job classes extend Resque\Job\Job.
• Decouple Tripod\Mongo\Jobs\JobBase from Tripod\Mongo\DriverBase
  • Extract LoggerTrait from DriverBase
  • Few methods from DriverBase used by jobs were re-implemented.
  • Make Tripod\Mongo\Jobs\JobBase extend Resque\Job\Job.
• Bump arc2 library
  • Allow versions 2 & 3.

[mike-dean-talis]

Looks good to an untrained tripod-ist.