Windowing algorithm for point multiplication

[SupremoUGH]

New:
manta-crypto:

• eclair::bool.rs: Added select_from_table function with default implementation to ConditionalSelect trait.
• algebra.rs: Added add_assign, double_assign and repeated_double_assign methods with default implementations to Group trait.
• algebra.rs: Added Window struct. The method scalar_mul implements windowed multiplication.
• algebra.rs: Added abstract correctness test window_multiplication_correctness for scalar_mul.

manta-pay:

• crypto::ecc::arkworks.rs: Implemented the PartialEq, ConditionalSelect and Zero traits from eclair for Group<C> and GroupVar.
• crypto::ecc::arkworks.rs: Added windowed_mul_is_correct test which tests a concrete implementation of Window for the native rust compiler.

Before we can merge this PR, please make sure that all the following items have been checked off:

• Linked to an issue with discussion and accepted design OR have an explanation in the PR that describes this work.
• Added one line describing your change in CHANGELOG.md and added the appropriate changelog label to the PR.
• Re-reviewed Files changed in the GitHub PR explorer.
• Checked that changes and commits conform to the standards outlined in CONTRIBUTING.md.

[BoyuanFeng]

some minor changes