Refactor v13 metadata types

[ascjones]

Replace custom definitions for errors and event metadata with scale-info type information for the pallet Event and Error types (depends on paritytech/scale-info#87 which adds documentation to the scale-info derive).

As @thiolliere pointed out, metadata for events and errors (which are expanded to simple enums) can be captured already by the scale_info derives.

Call definitions could also just use the scale-info derives on the Call enum also, but we will keep the custom types in case we need to add additional metadata, see the comment below.

Also:

• Renames types/comments with module -> pallet
• Adds wrapper types for calls and events metadata

[gui1117]

about calls I think it might makes sense to still organize it as metadata V12.

In the future we might want to add additional information per call variant. Like the origin the call can accept. Or just some unstructured information about the call. paritytech/polkadot-sdk#349

In this context having the call declared as a vec of function would allow use to just add another field in this FunctionMetadata.
On the other end we can still have an extra field in ModuleMetadata: calls_extra: Vec<FunctionMetadata> which only contains the additional information.

[ascjones]

Makes sense, so for events and errors just the TypeSpec is okay?

[gui1117]

Makes sense, so for events and errors just the TypeSpec is okay?

yes for me it makes sense considering those types are only description. But maybe opinion from other people using the metadata can be helpful here.

[gui1117]

looks good to me