Update APIs to use MobileCoinRng instead of RngSeed

[carybakker]

Soundtrack of this PR: A 'random' InSync song lol

Motivation

Sync up iOS and Android's implementation of idempotence for cross-platform compatibility

In this PR

• Deprecate the API calls for prepareTransaction that use RngSeed
• De-Deprecate the API calls that use MobileCoinRng
• Deprecated APIs will generate a new RNG from the seed, and then call the de-deprecated APIs with that RNG (all that part is done by the API client code on Android). Then for equivalency, when we receive an Rng via the de-deprecated APIs (that match Android in that they accept an Rng), we will generate a seed used to create a new ChaCha20Rng for the building of the output transaction (which will match Android once Android is updated to generate the seed before any other use).

[voloshyn]

would be great to have a test for this, @dolanbernard can you provide a test data from Android to cross-test?

[the-real-adammork]

not sure this is correct, if you only use the RNG to create a seed which you then pass around to see our internal RNG, that defeats the purpose of letting them pass in their own RNG class

[carybakker]

Android uses the input Rng to seed the RNG for output idempotence. So here, we are doing the same as Android with respect to the output transaction creation.

[the-real-adammork]

well then, doesnt seem to be as flexible as I initially thought, but if its the same as android thats correct

[the-real-adammork]

same feedback here

[carybakker]

same answer as above :)

[carybakker]

would be great to have a test for this, @dolanbernard can you provide a test data from Android to cross-test?

Test has been added with matching data (passing successfully)