[SEDONA-568] Refactor TestBaseScala to allow customizable Spark configurations

[zhangfengcdt]

• Added default Spark configurations in TestBaseScala trait.
• Provided a method defaultSparkConfig for default configurations.
• Allowed subclasses to override sparkConfig to add or modify Spark configurations.
• Updated initialization of Spark session and Spark context to use the provided configurations.
• Included comments to explain how to override configurations in subclasses.
• Ensured that default configurations are preserved if not overridden by subclasses.

Did you read the Contributor Guide?

• Yes, I have read the Contributor Rules and Contributor Development Guide

Is this PR related to a JIRA ticket?

• Yes, the URL of the associated JIRA ticket is https://issues.apache.org/jira/browse/SEDONA-568. The PR name follows the format [SEDONA-XXX] my subject.

What changes were proposed in this PR?

• Added default Spark configurations in TestBaseScala trait.
• Provided a method defaultSparkConfig for default configurations.
• Allowed subclasses to override sparkConfig to add or modify Spark configurations.
• Updated initialization of Spark session and Spark context to use the provided configurations.
• Included comments to explain how to override configurations in subclasses.
• Ensured that default configurations are preserved if not overridden by subclasses.

After this change, user can either use

• Default Configurations: Provided in defaultSparkConfig.
• Overriding Configurations: Subclasses can override sparkConfig and merge additional configurations with the default ones using the ++ operator, for example:

class CustomTest extends TestBaseScala {
  // Override sparkConfig to provide additional configurations
  override def sparkConfig: Map[String, String] = defaultSparkConfig ++ Map(
    "spark.sql.warehouse.dir" -> "/custom/warehouse/location",
    "spark.some.config.option" -> "some-value"
  )

  describe("CustomTest") {
    it("should use custom Spark configuration") {
      assert(sparkSession.conf.get("spark.some.config.option") == "some-value")
    }

    it("should access Spark context") {
      assert(sc != null)
    }
  }
}

How was this patch tested?

All existing unit tests should all pass without any impact.

Did this PR include necessary documentation updates?

• No, this PR does not affect any public API so no need to change the documentation.