Proposal: split auron-core module

[richox]

Is your feature request related to a problem? Please describe.
currently, Auron's code is tightly coupled to Spark. since we are planning to support more engines like Flink, we need an auron-core module to support a minimal working set of the native execution abilities.

Describe the solution you'd like

• decouple native engine code to Spark. for example, SparkUDFWrapper should be renamed to UDFWrapper.
• add auron-core maven module, which has JNI bridge, native execution wrapper, and a set of interfaces required by JNI. specified deps like Spark or Scala should be removed.
• auron-spark-extension module should be derived on auron-core with all interfaces implemented.

after all these task finished, we can support more engines from auron-core like auron-flink-extension.

Describe alternatives you've considered

Additional context

[Tartarus0zm]

great work!
Auron-core requires a higher level of abstraction to facilitate support for more engines in the future.

[merrily01]

Sounds like a great idea, I think this is worth exploring.