rename all `default_x`; sort out args; add default parameters

[bwanglzu]

Here is a checklist for this ticket

• [ ] rename default_traversal_paths to traversal_paths
• [ ] rename default_batch_size to batch_size
• [ ] keep the args in the order traversal_paths, batch_size, device, *args, **kwargs
• [ ] add default parameters for the endpoint functions, docs: Optional[DocumentArray] = None and parameters: Dict = {} and check whether the function can handle docs==None

[bwanglzu]

• [x] crafters #218
• [x] encoders-audio #219
• [x] encoders-video #219
• [x] encoders-image #220
• [x] encoders-text #221
• [ ] indexers-doccache
• [ ] indexers-merger
• [ ] indexers-searcher
• [ ] indexers-storage
• [x] rankers #218
• [x] segmenters #218

[nan-wang]

The following encoders are left for next week to avoid Breaking changes during the weekend.

• CLIPTextEncoder,
• TransformerTFTextEncoder,
• TransformerTorchEncoder
• CLIPImageEncoder

[CatStark]

Closing this one and we will create a new one for indexers after theOneIndexer is ready

The missing ones are:

• [ ] indexers-doccache
• [ ] indexers-merger
• [ ] indexers-searcher
• [ ] indexers-storage