Simplification: Merge load_from_metrics and load_from_checkpoint 
🚀 Feature
The two ways of loading a LightningModule from checkpoint only differ in one  argument, the tags_csv.
Motivation
The code is almost identical for both and the purpose is the same. If we merge these two into one function, it would simplify the API.
Pitch
Combine
load_from_metrics(cls, weights_path, tags_csv, map_location=None) and
load_from_checkpoint(cls, checkpoint_path, map_location=None) into a single signature:
load_from_checkpoint(cls, checkpoint_path, tags_csv=None, map_location=None)

and make load_from_metrics deprecated.
Alternatives
keep as is, not a big deal :)