Switch to new CodeCov uploader

The currently used bash uploader is deprecated and will be removed in
the future[1]. This commit replaces the existing setup with the new
uploader for all currently supported platforms as proposed in [2].

Additional notes:
- FreeBSD support isn't supported yet and keeps using the old uploader
- Moved the new implementation into a dedicated file `source`d by
  all coverage CI's (instead of changing each individual configuration)

[1] https://about.codecov.io/blog/codecov-uploader-deprecation-plan
[2] https://about.codecov.io/blog/introducing-codecovs-new-uploader

.azure-pipelines/windows.sh

@@ -134,11 +134,7 @@ CC="$CC" ./run --environment --jobs=$N "${targets[@]}" "${args[@]}"
 
 if [ "${DMD_TEST_COVERAGE:-0}" = "1" ] ; then
     cd $DMD_DIR
-    # CodeCov gets confused by lst files which it can't match
-    rm -rf test/runnable/extra-files test/*.lst
-    download "https://codecov.io/bash" "codecov.sh"
-    bash ./codecov.sh -p . -Z
-    rm codecov.sh
+    OS_NAME=windows source ci/codecov.sh
 
     # Skip druntime & phobos tests
     exit 0