add --state flag feature to dbt integration

[dlawin]

Adds a new flag --state for use with the dbt integration

A user can use this flag to specify the "production" manifest location e.g.:
data-diff --dbt --state ~/prod_manifest.json

This removes the need for configuration in the dbt_project.yml, and covers scenarios not covered via configuration. The prod manifest is used as the source of truth for production model locations vs. via configuration.

Changes:

• added prod_manifest_obj to DbtParser
• renamed manifest_obj in DbtParser to dev_manifest_obj to differentiate
• Renamed DbtParser.get_datadiff_variables to DbtParser.get_datadiff_config (this was easily confused with _get_diff_vars)
  • Altered to return a TDatadiffConfig object vs. the previous dictionary
• get_manifest_obj altered to be generic (can be used for any path)
• _get_diff_vars altered to construct prod path based the production manifest when it is present
  • new method for manifest _get_prod_path_from_manifest
  • moved existing config functionality to new method _get_prod_path_from_config
• DataDiffDbtProjectVarsNotFoundError now thrown when config is not present AND not using --state

Resolves #454