test/browser: run tests inside the tasks container

This simplifies the "outside" setup quite a bit and gives us the same
tasks container that test runs on the Cockpit CI run under.

This change also implicitly changes the test browser to chromium (which
is no longer an issue — we just use it from the tasks container).

test/browser/main.fmf

@@ -2,14 +2,9 @@ summary:
     Run browser integration tests on the host
 require:
   - cockpit-starter-kit
+  - podman
   - cockpit-ws
   - cockpit-system
-  - bzip2
-  - git-core
   - glibc-langpack-de
-  - libvirt-python3
-  - make
-  - npm
-  - python3
 test: ./browser.sh
 duration: 60m