Limit tab completion of scan command to scans with installed components (#74)

* scans without installed requirements dont tab-complete

* added meets_requirements functions to classes

* updated tests

* added check for None case

tests/test_shell/test_recon_pipeline_shell.py

@@ -428,12 +428,17 @@ class TestReconShell:
             "webbrowser.open", autospec=True
         ) as mocked_web, patch("selectors.DefaultSelector.register", autospec=True) as mocked_selector, patch(
             "cmd2.Cmd.select"
-        ) as mocked_select:
+        ) as mocked_select, patch(
+            "pipeline.recon-pipeline.get_scans"
+        ) as mocked_scans:
+
             mocked_select.return_value = "Resume"
             mocked_popen.return_value = process_mock
 
             test_input += f" --results-dir {tmp_path / 'mostuff'}"
 
+            mocked_scans.return_value = {"FullScan": ["pipeline.recon.wrappers"]}
+
             if db_mgr is None:
                 self.shell.do_scan(test_input)
                 assert expected in capsys.readouterr().out