MantaPay v1

[SupremoUGH]

Last part of #153. It consists of the changes related to the transfer protocol and the signer.

Changes:
manta-util:

• codec.rs: Encode implementation for manta_util::Array.
• num.rs: CheckedAdd implementation for references of types implementing CheckedAdd. Same for CheckedSub.

manta-crypto:

• arkworks::algebra: moved ScalarVar, Group, and GroupVar and their trait implementations here.
• constraint: Added division with remainder utilities.
• encryption: Fixed error in Constant implementation for UnsafeNoEncrypt.

manta-accounting:

• asset.rs: Weakened the assumptions for HashAssetMap and BTreeAssetMap.
• transfer: Upgrade to new transfer protocol.
• wallet: Upgrade signer.

manta-pay:

• crypto::ecc: Deleted and moved to manta-crypto.
• crypto::poseidon::arkworks: Fixed error in BlockElement implementation for FpVar.
• crypto::poseidon::encryption: Fixed error in Write implementation for CiphertextBlock. Added Decode and Encode implementations for FixedEncryption.
• crypto::poseidon: Implementations for State.
• config: Concrete implementations of transfer::Configuration and protocol::Configuration in mod and utxo, respectively.
• signer: Upgrade to the new signer.
• test and simulation: new testing suite and simulation for the new protocol.

manta-parameters and manta-pay::parameters:

• update the parameters to the new protocol.

manta-benchmark:

• benchmarking suite for ToPrivate, PrivateTransfer and ToPublic proof generation and verification.

TODO:

• Revisit the re-implementations of Sample (which I might have to undo).
• Update the branch in manta-parameters to main.
• Move some tests in manta-accounting to manta-pay (if possible).

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