Tricrypto price oracle and lp price

[allt0ld]

Description

Closes #230.

• Implemented Tricrypto_NG's oracle behavior in CurveCryptoPool (slight differences from 2-coin implementation)
• Enabled 3-coin lp_price for CurveCryptoPool imported from pool.cryptoswap.calcs.tricrypto_ng.

Hygiene checklist

• [x] Changelog entry
• [x] Everything public has a Numpy-style docstring (modules, public functions, classes, and public methods)
• [x] Commit history is cleaned-up with minor changes squashed together and descriptive commit messages following Tim Pope's style

Cute Animal Picture

[github-actions[bot]]

Coverage report

The coverage rate went from 75.61% to 76.08% :arrow_up: The branch rate is 62%.

95.83% of new lines are covered.

Diff Coverage details (click to unfold)

### curvesim/pool/cryptoswap/pool.py `94.11%` of new lines are covered (`90.21%` of the complete file). Missing lines: `1014` ### curvesim/pool/cryptoswap/calcs/factory_2_coin.py `100%` of new lines are covered (`85.71%` of the complete file). ### curvesim/pool/cryptoswap/calcs/__init__.py `100%` of new lines are covered (`87.5%` of the complete file). ### curvesim/pool/cryptoswap/calcs/tricrypto_ng.py `100%` of new lines are covered (`90.26%` of the complete file).