add config-interface crate

[kevinheavey]

Problem: some crates (particularly solana-account-decoder) depend on solana-config-program, which is very heavy because it depends on solana-program-runtime.

Solution:

• rip out everything except the processor and date_instruction.rs (deprecated and doesn't seem to be used elsewhere).
• make serde and bincode optional in the new crate

Once this is published we would then replace the relevant code in agave/programs/config with re-exports

[joncinque]

This makes sense to me, thanks! Can you move this PR to https://github.com/solana-program/config instead though?

[buffalojoec]

The existing client in https://github.com/solana-program/config does not depend on solana-program-runtime.

[kevinheavey]

It depends on solana-program though

[febo]

I think we can follow the same approach of solana-program/system and solana-program/stake – i.e., have an interface crate alongside the clients and program.

[joncinque]

Can this be closed since solana-program/config#47 landed?