[IMP] core, web: test failure reporting

* remove misleading documentation about a "test failed" message, in
  13.0 any uncaught exception or console.error will cause the current
  test to be interpreted as failed
* fix tour manager to console.error its step and not add a second
  useless error message
* fix menu tester to try and display the failure cause on failure
* improve qunit's test reporter to print the number of tests failed in
  case of test suite failure

Should make test failures in tours a bit clearer.

closes odoo/odoo#44296

X-original-commit: 78121b68
Signed-off-by: Xavier Morel (xmo) <xmo@odoo.com>