feat: add no_std support for nonce-account crate

[sonicfromnewyoke]

Problem

solana-nonce-account crate has no no_std support

Summary of Changes

• add crate level attribute
• replace import of std::cell::RefCell with core::cell::RefCell

[febo]

I think we need to make its dependencies no_std first. For example:

solana-account = { workspace = true, features = ["bincode"] }

bincode is "std" by default, so probably won't work as it is.

Note: I didn't mean to close the PR.