[zk-token-proof] Add functionality to read proof from accounts instea…

…d of instruction data (solana-labs#34750)

* add functionality to read proof from accounts instead of instruction data

* update add tests

* clippy

* clarify instruction data discriminator

* avoid cloning entire proof data

* Update programs/zk-token-proof/src/lib.rs

Co-authored-by: Jon C <[email protected]>

* update `PROOF_OFFSET_LENGTH` to `INSTRUCTION_DATA_LENGTH_WITH_PROOF_ACCOUNT`

* update instruction docs

* add feature gate

* Update sdk/src/feature_set.rs

Co-authored-by: Jon C <[email protected]>

* update feature name `enable_zk_from_account` to `enable_zk_proof_from_account`

* Apply suggestions from code review

Co-authored-by: Jon C <[email protected]>

* clarify the instruction data length more precisely

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Co-authored-by: Jon C <[email protected]>