Split Linux ASAN and MinGW tests across runners

The Linux Meson 64-bit and Windows MinGW jobs often determine CI
latency because their test suites take much longer than their cached
builds.

Split each test suite across two runners while running the setup suite
on both.  Use Meson's native --slice support for MinGW.  The Linux CI
image has Meson 1.7, so derive a deterministically sorted test list
there instead of using the Meson 1.8 --slice option.

Use separate failure-log artifact names for matrix jobs.  Share the
slice-specific upload step with the existing Windows Visual Studio
matrix, whose jobs otherwise use the same artifact name.

Author: x4m

.github/workflows/pg-ci.yml

@@ -625,17 +625,24 @@ jobs:
   # - Uses address sanitizer, (sanitizer failures are typically printed in the
   #   server log). We test asan with meson rather than autoconf, as it's a bit
   #   faster at running the tests.
+  # - Splits the tests across two runners
   # - Uses io_method=io_uring
   # - Uses meson feature autodetection
   linux-meson-64:
-    name: Linux - Meson (64-bit)
+    name: Linux - Meson (64-bit) - Slice ${{ matrix.slice}}/${{ matrix.num_slices}}
     needs: [setup, sanity-check]
     if: *linux_job_if
     runs-on: *linux_runs_on
     container: *linux_ci_container
     timeout-minutes: 60
     env: *linux_env
 
+    strategy:
+      fail-fast: false
+      matrix:
+        num_slices: [2]
+        slice: [1, 2]
+
     steps:
       - name: Update Environment
         env:
@@ -668,10 +675,47 @@ jobs:
 
       - name: Test world
         shell: *su_postgres_shell
-        run: *meson_test_world_cmd
+        run: |
+          ulimit -c unlimited
+
+          echo ::group::test_setup
+          meson test ${{env.MTEST_ARGS}} --suite setup --logbase setup || exit 1
+          echo ::endgroup::
+
+          # The system Meson is older than 1.8, which introduced --slice.
+          # Emulate its round-robin slicing using the test list instead.
+          readarray -t test_names < <(
+            meson test ${{env.MTEST_ARGS}} ${{env.MTEST_TARGET}} \
+              --list --no-suite setup |
+            sort |
+            awk -F ' - ' \
+              -v slice=${{ matrix.slice}} \
+              -v slices=${{ matrix.num_slices}} \
+              '(NR - 1) % slices == slice - 1 {
+                 name = $NF
+                 sub(/:[^ ]+ \/ /, ":", name)
+                 print name
+               }'
+          )
+          meson test ${{env.MTEST_ARGS}} \
+            --num-processes ${{env.TEST_JOBS}} \
+            --no-suite setup "${test_names[@]}"
 
       - *linux_collect_cores_step
-      - *upload_logs_step
+      - &upload_logs_sliced_step
+        name: Upload logs
+        if: failure() && !cancelled()
+        uses: actions/upload-artifact@v7
+        with:
+          name: logs-${{ github.job }}-${{ matrix.slice }}-${{ github.run_id }}-${{ github.run_attempt }}
+          path: |
+              **/*.log
+              **/*.diffs
+              **/regress_log_*
+              **/crashlog-*.txt
+              build/meson-logs/**
+              **/config.log
+          if-no-files-found: ignore
 
 
   # Job: macOS - Meson
@@ -1024,19 +1068,28 @@ jobs:
             call "C:\Program Files\Microsoft Visual Studio\2022\Enterprise\VC\Auxiliary\Build\vcvarsall.bat" x64
         run: *meson_test_world_cmd
 
-      - *upload_logs_step
+      - *upload_logs_sliced_step
 
 
   # Job: Windows - MinGW - Meson
   windows-mingw:
-    name: Windows - MinGW - Meson
+    name: Windows - MinGW - Meson - Slice ${{ matrix.slice}}/${{ matrix.num_slices}}
     needs: [setup, sanity-check]
     if: |
       !cancelled() &&
       needs.setup.outputs.mingw == 'true' &&
       needs.sanity-check.result != 'failure'
     runs-on: windows-2022
     timeout-minutes: 60
+
+    # MinGW is generally one of the slowest CI jobs.  Split its tests across
+    # two runners, as is already done for the Visual Studio job.
+    strategy:
+      fail-fast: false
+      matrix:
+        num_slices: [2]
+        slice: [1, 2]
+
     env:
       # Avoid port conflicts between concurrent tap tests
       PG_TEST_USE_UNIX_SOCKETS: 1
@@ -1140,9 +1193,11 @@ jobs:
       - *ccache_save_step
 
       - name: Test world
+        env:
+          MTEST_TARGET: --slice ${{ matrix.slice}}/${{ matrix.num_slices}} ${{env.MTEST_TARGET}}
         run: *meson_test_world_cmd
 
-      - *upload_logs_step
+      - *upload_logs_sliced_step
 
 
   # Job: CompilerWarnings