feat: Remove unencryptedDataKeyLength

[seebees]

It is a feature that is not being used.
This was created to let callers confirm that the unencrypted data key matched the algorithm suite,
but this checking is done directly into the cryptographic material now.
The hasUnencryptedDataKey is the best way to check for existence,
and the materials themselves will ensure that algorithm suite specifications are meet.

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[mattsb42-aws]

LGTM with the understanding that this represents a breaking change and that needs to be reflected in the next release version.

[seebees]

NOTE: This breaking change is ONLY done because the project is in beta.
Otherwise there would be a major version bump.