fix confusing azure pipelines status for coverage

The coverage report was always the final section of the main test run.
This made it hard to scroll around and find exactly what went wrong --
particularly as not everyone realizes that coverage isn't part of the
test run, but also because the output from coverage is... excessively
long.

This mirrors what we do in our other workflows.

azure-pipelines.yml

@@ -112,3 +112,8 @@ jobs:
       filePath: .\ci\run.ps1
     env:
       MESON_CI_JOBNAME: azure-$(System.JobName)
+  - task: PowerShell@2
+    displayName: Gathering coverage report
+    inputs:
+      targetType: 'filePath'
+      filePath: .\ci\coverage.ps1

ci/coverage.ps1

@@ -0,0 +1,14 @@
+echo ""
+echo ""
+echo "=== Gathering coverage report ==="
+echo ""
+
+python3 -m coverage combine
+python3 -m coverage xml
+python3 -m coverage report
+
+# Currently codecov.py does not handle Azure, use this fork of a fork to get it
+# working without requiring a token
+git clone https://github.com/mensinda/codecov-python
+python3 -m pip install --ignore-installed ./codecov-python
+python3 -m codecov -f .coverage/coverage.xml -n "VS$env:compiler $env:arch $env:backend" -c $env:SOURCE_VERSION

ci/run.ps1

@@ -98,21 +98,4 @@ echo "=== Start running tests ==="
 # does that by default so we need to forward it.
 cmd /c "python 2>&1 ./tools/run_with_cov.py  run_tests.py --backend $env:backend $env:extraargs"
 
-$result = $LastExitCode
-
-echo ""
-echo ""
-echo "=== Gathering coverage report ==="
-echo ""
-
-python3 -m coverage combine
-python3 -m coverage xml
-python3 -m coverage report
-
-# Currently codecov.py does not handle Azure, use this fork of a fork to get it
-# working without requiring a token
-git clone https://github.com/mensinda/codecov-python
-python3 -m pip install --ignore-installed ./codecov-python
-python3 -m codecov -f .coverage/coverage.xml -n "VS$env:compiler $env:arch $env:backend" -c $env:SOURCE_VERSION
-
-exit $result
+exit $LastExitCode