Save SPIDER tests data on disk, rather than to memory

I've encountered this strange behaviour, staring with MariaDB 10.5.20.
The SPIDER tests, and only them, started to fail in 100% cases on all arches
with wide range of "no space left on device" like errors.

This is interesting, as simmilar issues occured before
only on specific arches or build systems.

I've thought that maybe the full suite, which run before the spider tests,
have left over some data in the memory which would leave less space for the
spider tests.
However swapping order - running the spider test first and the full suite
later didn't help anyhow. The spider tests failed rightaway.

Also, it's interesting that running just the main suite in memory is possible.
This observation should rule out changes in the build system (lowering the
memory limits for builders), as I'd expect that the main suite woould have much
bigger memory need than the spider tests.

--

This leads to a possibility that there is actually a bug in the spider engine
or tests, which cause the unexpected larger memory consumption.
This should be examined further. Sadly I don't have capacity for it now.

mariadb.spec

@@ -1243,7 +1243,7 @@ export MTR_BUILD_THREAD=$(( $(date +%s) % 1100 ))
       --skip-test-list=unstable-tests
     %endif
     # Second run for the SPIDER suites that fail with SCA (ssl self signed certificate)
-    perl ./mysql-test-run.pl $common_testsuite_arguments --skip-ssl --big-test --mem --suite=spider,spider/bg,spider/bugfix,spider/handler \
+    perl ./mysql-test-run.pl $common_testsuite_arguments --skip-ssl --big-test --suite=spider,spider/bg,spider/bugfix,spider/handler \
     %if %{ignore_testsuite_result}
       --max-test-fail=999 || :
     %endif