Attempt to remove csc and lift all calls to the root of the api object <major>

[lakardion]

Right now every time we define a custom call we have to go within csc or customServiceCalls key which might be a bit of an overhead in terms of DX, and a bit confusing for initial lib users.
With this change the idea is to surface all the custom methods to the root of the api object so there's no field in the way for using these custom calls.

Something to consider when implementing this is that we will have to ban keys that are being currently used in the api root object:
So custom service calls should not be able to be called:

• create
• list
• update
• remove
• client