calcite-avatica: Transition to Ideal Integration (Upstream Source)

[vishalcoc44]

All 6 deep fuzzers have been upstreamed to the apache/calcite-avatica repository. Consequently, this PR removes the redundant local fuzzer source files from this repository and updates the build configuration to utilize the the upstream project's build system.

Changes:

1. Upstream Integration: Updated the Dockerfile to clone the official Apache Calcite Avatica repository instead of using local files.
2. Dynamic Fuzzer Discovery: Rewrote build.sh to leverage the upstream Gradle build process. It now dynamically discovers all fuzzer classes in the org.apache.calcite.avatica.fuzz package. This allows for new fuzzers added upstream to be automatically included in the OSS-Fuzz build without further configuration changes here.
3. Clean Configuration: Removed local fuzzer source files (ConnectStringParserFuzzer.java, Base64Fuzzer.java) to establish a clean upstream-sync workflow.

In process of adding fuzzers has been as told in this pr apache/calcite-avatica#300

[github-actions]

vishalcoc44 is a new contributor to projects/calcite-avatica. The PR must be approved by known contributors before it can be merged. The past contributors are: hunsche, arthurscchan