[Improvement] Change the storage format of a .syndicate in S3 Bucket

[bohdan-onsha]

Change the storage format of a .syndicate file in S3 Bucket from Python Obj to YAML Obj

Current state of the .syndicate file in AWS S3:

!!python/object:syndicate.core.project_state.project_state.ProjectState

_dict:

  build_projects_mapping:

    python: src

  events:

[dmytro-afanasiev]

https://github.com/epam/aws-syndicate/pull/183