Move all state variables into environment within package

[atharvashahane28]

This PR will:

• Create config environment and assign default values to it.
• Move most of the items in in globals.R to config by adding a prefix config$ when assigning and retrieving them. If there's any chance it would change in a different deployment it should be in config and not defined as a global constant in the package.
• Move state variables created by set_s3_config and retrieved by get_s3_config to the config environment. Replace assign() with config$option <- .
• Add Items in config to set:
  • local_temp_path
  • log_file_path,
  • log (flag to turn logging on and off)
• Update logging to honor log_file_path and log
• Update flow to honor local_temp_path
• Move set_s3_config and get_s3_config into s3_config.R (from flow.R)
• Set all list items as variables in config using config$...