program: Remove usage of stake::config

[joncinque]

Recreated from solana-labs/solana-program-library#6542

Problem

The stake::config account has been fully and removed with anza-xyz/agave#470, but the single pool program still uses and relies on it.

Solution

Once the 2.0 crates are available and SPL uses them, remove all references to and usage of stake::config.

[programskillforverification]

Hi, could you assign this one to me?

[joncinque]

Hi @programskillforverification , we don't assign issues to outside contributors. The code is open source though, so feel free to send in a pull request!

[2501babe]

my current thinking is after the bpf stake program has solana-program/stake#53 i will update this to do this same thing: skip stake config and all sysvars if passed in as accounts, remove them all from instruction builders

[joncinque]

Makes sense to me!