[suggestion] Split generic configuration functionality from iroha_config_base into a standalone library

[0x009922]

Description

Currently, iroha_config and iroha_client::config contain a lot of boilerplate and based on general types/helpers from iroha_config_base. The intention was to develop a separate configuration library which will provide convenient abstractions and macros to define a flexible configuration system.

Such a library should provide the following:

• Useful errors:
  • Fancy diagnostic messages with spans to the source and hints
  • Emit as many errors as possible at once
• Tracing: it should be possible to print information about which were read from a source, how they are overwritten etc. See the RFC for more details: Tracking Issue for Configuration Overhaul #2585

I was working on a draft of it: https://github.com/0x009922/project-soukousei. It's far from being finished. I used schematic as reference, but unfortunately it has some design decisions I strongly dislike.

Also

• Remove merge dependency #4298
• Enhance configuration errors #4299
• Implement config tracing #4300