Support Oracle upsert semantics in MLSQLJDBC

[chncaesar]

What changes were proposed in this pull request?

To support Oracle upsert semantics.

• Add OracleUpsertBuilder to generate merge into statement
• Put some logic of MySQLUpsertBuilder.upsertStatement into a separate function to better support unit test
• Add two unit tests in UpsertBuilderTest

How was this patch tested?

• Unit test passed. Class: UpsertBuilderTest.scala
• Integration test on local mode pased.
  oracle jdbc upsert test
  

mysql jdbc upsert test

Oracle jdbc jar used during test

        <dependency>
            <groupId>com.oracle.database.jdbc</groupId>
            <artifactId>ojdbc8</artifactId>
            <version>21.3.0.0</version>
        </dependency>

Are there and DOC need to update?

• Documentation will be provided in byzer-doc repo

Spark Core Compatibility

Compatible with Spark 2.4 & 3.0

Issue #1718