ci: increase functional test concurrency from 8 to 16

Now that there are no bottlenecks we can increase the concurrency of the
tests.

This speeds up functional test runs by 20-30% in average.

| host     | before (s) | after (s) | change |
|----------|------------|-----------|--------|
| m7g 5.10 |        195 |       161 |   -18% |
| m7g 6.1  |        225 |       172 |   -24% |
| m5n 5.10 |        466 |       274 |   -40% |
| m5n 6.1  |        440 |       291 |   -33% |

Signed-off-by: Pablo Barbáchano <[email protected]>

Author: pb8o

.buildkite/pipeline_cross.py

@@ -85,7 +85,7 @@
                 f"buildkite-agent artifact download snapshots/{src_instance}_{src_kv}.tar .",
                 f"tar xSvf snapshots/{src_instance}_{src_kv}.tar",
                 *pipeline.devtool_test(
-                    pytest_opts=f"-m nonci -n4 {k_val} integration_tests/functional/test_snapshot_restore_cross_kernel.py",
+                    pytest_opts=f"-m nonci -n8 --dist worksteal {k_val} integration_tests/functional/test_snapshot_restore_cross_kernel.py",
                 ),
             ],
             "label": f"🎬 {src_instance} {src_kv} ➡️ {dst_instance} {dst_kv}",

.buildkite/pipeline_pr.py

@@ -76,7 +76,7 @@
     pipeline.build_group(
         "⚙ Functional and security 🔒",
         pipeline.devtool_test(
-            pytest_opts="-n 8 --dist worksteal integration_tests/{{functional,security}}",
+            pytest_opts="-n 16 --dist worksteal integration_tests/{{functional,security}}",
         ),
     )