ci: add core Apache Cloudberry (incubating) build and test workflow

[edespino]

Introduces foundational GitHub Actions workflow for Apache Cloudberry (incubating) CI:

• Multi-stage build pipeline with skip detection
• Rocky Linux 9 containerized build environment
• RPM packaging and source tarball generation
• Installation verification
• Test matrix for core regression tests (subset starting point)
• Detailed test result parsing and reporting
• Comprehensive artifact management

The workflow provides:

• Clean build environment for each run
• Consistent test execution framework
• Automated installation testing
• Test result aggregation
• Clear job dependencies and progression
• Flexible CI skip mechanisms

Due to inconsistent test runs, disable the following from greenplum_schedule:

• cbdb_parallel
• instr_in_shmem_verify

This commit establishes the initial CI pipeline for Apache Cloudberry (incubating) with future test matrix expansion planned.

[tuhaihe]

To merge this PR, we'd better email "users@infra.apache.org" to request the Infra team bypass the old checks.

[yihong0618]

Amazing work...learned something, thanks

[Baowen648]

Really efficient work here! You’ve solved the problem with the least amount of code needed.