Extend `GetCallMetadata` with indices

[ggwpez]

GetCallMetadata can currently be used to get the call- and module-name of a RuntimeCall.
In cases where we want to select specific calls/modules, it is better to use their index than strings.

GetCallMetadata could therefore be extended to also return these indices. Looking internally, we use a GetCallName trait which is re-used in the GetCallMetadata trait. So probably analogous to that add a GetCallIndex and then re-use that as well.

[kziemianek]

Hi, I would love to do it :)

[ggwpez]

Okay great! yes please go ahead

[kziemianek]

@ggwpez, I think I have most of stuff done, but I'm struggling to figure out how to get function index from decl_module! macro (frame/support/src/dispatch.rs). I need this to fill GetCallIndex trait implementation. Could you guide me a little bit ?

[ggwpez]

Yes best to open a Draft MR @kziemianek, then it is easier to collaborate and comment.

[kziemianek]

@ggwpez I've opened, please take a look.

[liamaharon]

Closed in paritytech/substrate#13558

[ggwpez]

Closed in paritytech/substrate#13558

That was just the first part. The second part is blocked on removing the old decl_* pallet macros.