feat: add comprehensive user guide for bigdata-test

- Introduced a detailed user guide in Asciidoc format with examples for JUnit, Spring Boot, and Spark.
- Documented module structure, dependency management, and programmatic usage of `BigDataTestKit`.
- Included instructions for configuring Kerberos, S3 JCEKS, Kafka Avro seeding, and HMS-backed tables.
- Added troubleshooting section for common issues with containerized services and external tables.
- Enhanced readability with table-based representations of configuration options and service flags.

Author: CoderYellow