Add packs and queries from input

This commit adds the packs and queries from the actions input to the
config file used by the CodeQL CLI.

When the `+` is used, the actions input value is combined with the
config value and when it is not used, the input value overrides the
config value.

This commit also adds a bunch of integration tests for this feature.
In order to avoid adding too many new jobs, all of the tests are
run sequentially in a single job (matrixed across relevant operating
systems and OSes).

.github/workflows/__split-workflow.yml

@@ -63,6 +63,7 @@ jobs:
         output: ${{ runner.temp }}/results
       env:
         TEST_MODE: true
+
     - name: Assert No Results
       shell: bash
       run: |