[TASK] Support specifying the crate name in context derive macros

[Serial-ATA]

Overview

I'd like to do the following:

sdk = { git = "https://github.com/tangle-network/blueprint", package = "blueprint-sdk" }

But the context derive macros assume that I am using blueprint-sdk:

https://github.com/tangle-network/blueprint/blob/8d98a472142b47680142d3bdfdcdacd5e02d0a29/crates/macros/context-derive/src/keystore.rs#L25

We should have a helper attribute to allow you to specify the crate name.