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

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

Cute Animal Picture

[github-actions]

Coverage report

The coverage rate went from 75.61% to 76.08% ⬆️
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).

[chanhosuh]

Very nice overall! Sorta nitpicks, but it's an important point about style.