support optional tags argument to select source tables to stage

[jean-estime]

Description & motivation

Usability improvements to source table selection by supporting an optional tags argument.

Feature benefits:

• ability to maintain a short hand way of selecting sources via the 'tags' attributes in the source config and source tables
• ability to refresh tables across multiple sources without having to:
• • list a large number of tables with the select argument
• • create/refresh every table defined in a source because its shorter than listing tables with the select argument
• • create/refresh all sources because they are dispersed across multiple sources and it is easier to just run all external tables

Checklist

• [x] I have verified that these changes work locally
• [x] I have updated the README.md (if applicable)
• [x] I have added an integration test for my fix/feature (if applicable)

[jean-estime]

@jeremyyeo any value in this feature being a part of this package? We have a wrapper for it in our dbt project.