Global cast configuration

[Arcticae]

Which components does the task require to be changed? (think hard pls)

sncast

Description

We should consider adding a global config (perhaps like a global snfoundry.toml) that would keep our configuration which is relevant not only to one project, but also in different other contexts:

• RPC URLs
• accounts
• used block explorer
• defaults for those values

This would mean that we'd deprecate usage of profiles in favour of those, while adding a flag to declare/script for explicit "scarb profile" definition (now defaults to dev if custom profile is not release or dev).

The behavior of this should be described in a design doc, with an example usage and case study.

Related: #2212 #2220 #2218

[cptartur]

We should address the issue of the interaction between local configs and global config in the design document.