Upgrade Solana to 2.1.0

[acheroncrypto]

Problem

CI has a bunch of errors after the release of Solana v2.1.0 crates.

error: package `solana-program v2.1.0` cannot be built because it requires rustc 1.79.0 or newer, while the currently active rustc version is 1.75.0-dev
Note that this is the rustc version that ships with Solana tools and not your system's rustc version. Use `solana-install update` or head over to https://docs.solanalabs.com/cli/install to install a newer version.
Either upgrade to rustc 1.79.0 or newer, or use
cargo update solana-program@2.1.0 --precise ver
where `ver` is the latest version of `solana-program` supporting rustc 1.75.0-dev

Summary of changes

Upgrade Solana crates and tooling to 2.1.0.

spl-token-confidential-transfer-proof-generation currently needs to be patched to make it compatible with Solana v2.1.0 crates. See solana-labs/solana-program-library#7416 (comment) for details about the problem.

Note: The goal of this PR is to fix the CI issues in this repository, and the version requirement for various Solana crates are unchanged (still ^2), meaning it's still possible to use Anchor with Solana versions earlier than 2.1.0.

[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.