Store IDL on-chain at deterministic address

[brewmaster012]

https://www.anchor-lang.com/docs/cli#idl

Anchor framework has an notion of storing IDL file onchain on a determinstic address so that
anyone can fetch the IDL of an on-chain program using its program ID.

This enhances interactions for clients to interact with the solana program, a limited version of
Etherscan's verified contract and its ABI storage. The difference is that the IDL is stored onchain.