[DNM][CI] Debug spark-test-spark41 SIGSEGV in NativeBackendInitializer

[jackylee-ch]

What changes were proposed in this pull request?

DNM — Debug-only PR for issue #12534.

spark-test-spark41 / spark-test-spark41-slow fail consistently on every recent Velox Backend (x86) run. The forked surefire JVM dies with SIGSEGV (exit 134) while running ColumnarBatchTest (the first VeloxBackendTestBase-based suite), inside native backend initialization:

siginfo: si_signo: 11 (SIGSEGV), si_code: 1 (SEGV_MAPERR), si_addr: 0x0000000000000030
C  [libgluten.so+0xdb73a4]
j  org.apache.gluten.init.NativeBackendInitializer.initialize(...)
j  org.apache.gluten.backendsapi.velox.VeloxListenerApi.initialize(...)
j  org.apache.gluten.test.VeloxBackendTestBase.setup()

(hs_err captured via the diagnostics steps borrowed from #12551's run.)

This PR trims velox_backend_x86.yml to only build-native-lib-centos-7 + the two spark41 jobs, and adds crash-diagnostics steps (print/upload hs_err_pid*.log, surefire *.dumpstream, cores) so we can iterate quickly and bisect the cause.

How was this patch tested?

CI only.