cli: Add ability to override toolchain from Anchor.toml

[acheroncrypto]

Problem

Switching Anchor and Solana versions between repositories is cumbersome.

Summary of changes

• Add toolchain property for Anchor.toml to override current toolchain versions(verifiable builds also use this)

[toolchain]
anchor_version = "0.28.0"
solana_version = "1.16.0"

[vercel]

@acheroncrypto is attempting to deploy a commit to the coral-xyz Team on Vercel.

A member of the Team first needs to authorize it.