github: rename unit tests action to just tests

a lot of those tests are not unit tests and calling
those 'unit tests' is confusing

Signed-off-by: Christoph Ostarek <christoph@zededa.com>

.github/workflows/unit.yml → .github/workflows/tests.yml

@@ -1,5 +1,5 @@
 ---
-name: Unit tests
+name: Tests
 on:  # yamllint disable-line rule:truthy
   push:
     branches: