This adds CSV support to idf_size.py and idf.py size actions and using the --format argument which accepts 'text', 'json' or 'csv' as input.
idf_size.py --json argument is deprecated but left to avoid a breaking change.
For idf.py size actions OUTPUT_JSON environment variable set at configuration time is overriden at target build time if --format is used.
Additionally, this commit refactors big parts of code, unified usage of json_dict and manually generated dictionaries for textual output and improves code quality in many parts.
