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(Tracking issue for #[doc(cfg(…))], #[doc(cfg_hide(…))] and doc_auto_cfg rust-lang/rust#43781).

[vercel]

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

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