Enable all features for docs.rs build

[acheroncrypto]

Problem

docs.rs build only shows default features. For example, metadata module of anchor-spl is not shown.

Summary of changes

• Enable all features for docs.rs build
• Enable doc_auto_cfg feature for docs.rs build to automatically annote features. This feature is only enabled for docs.rs build because it's currently not stable(rustdoc: Tracking issue for #[doc(cfg)] and automatically documented #[cfg]s rust-lang/rust#43781).

[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.