[Suggestion] Docs for on subtensor calls

[chideraao]

From Roman

We need to create a document that describes the concept of a call (GenericCall).
What am I talking about?
We already have a lot of functionality that accepts call argument:
Proxy extrinsics
One of Crowdloan extrinsic
More complex MeV Shield logic is on the way (this will also require doc. Const expects this logic to be released next week)
get_extrinsic_fee methods
Users will have to create a call to pass as an argument. But I'm getting dozens of questions about this.

SDK has a CallBuilder implementation for all Subtensor pallets functions we use. This makes life easier if the user understands the concept. Otherwise, it becomes completely unclear. I believe two things need to be done:
improve the usability of CallBuilder in the SDK and move imports to the package root level (this is my responsibility);
create doc/s describing the general concept of using GenericCall and its usage in related SDK extrinsics inclused CallBulder classes usage (this task is on you dear document writers, but I'm happy to help with examples). I guarantee, if we will not produce such a document, theme community comes with so many questions.

Also, a link to this document can be added to extrinsics doctrings and to docs describing Proxy, Crowdloan, MeV Shield, and other future docs that for new logics which accepts call as an argument.