Update CI action (#565)

* Fix action job name
* Make nose generate coverage.xml directly
* Use codecov flags to differentiate all matrix dimensions

.github/workflows/ci.yml

@@ -3,7 +3,8 @@ name: Continuous Integration
 on: [push, pull_request]
 
 jobs:
-  Tests & Coverage:
+  tests_coverage:
+    name: Tests & Coverage
     runs-on: ${{ matrix.os }}
     strategy:
       matrix:
@@ -45,5 +46,9 @@ jobs:
           nosetests
           build/lib/pysb
           --with-coverage --cover-inclusive --cover-package=build/lib/pysb
+          --cover-xml
           -a '!gpu'
       - uses: codecov/codecov-action@v3
+        with:
+          verbose: true
+          flags: os-${{ matrix.os }},python-${{ matrix.python-version }}