Make the Adam optimization optional and learning rate/epochs configurable in DragonNet

[jeongyoonlee]

Proposed changes

This PR fixes #600. As @matthewvowels1 proposed, it makes the Adam optimization step optional and learning_rate and epochs configurable for both Adam and SGD in DragonNet.

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Further comments

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[jeongyoonlee]

Currently, CI fails due to the dependency issue between numba and latest numpy (ref: numba/numba#8718).

I tested this PR with numba==0.55.2, numpy==1.22.4, shap==0.41.0 and all 79 unit tests as well as the DragonNet example notebook finished successfully.

[paullo0106]

LGTM