[IMP] tests: replace browser_js success and failure strings

When evaluating js tests using the browser_js method, they are
considered a success when 'ok' is found in the console log and a failure
if 'error' is found instead.

This is not very robust and recently failed with this commit : 7410de11
It adds a filter named 'Error' in a view, when the 'click_all' test
clicks on this filter, a message with the name of the filter is written
in the console, wrongly leading to a test failure.

With this commit, the browser_js method expects a log message in the
browser console with the explicit text "test successful".
On the other hand, any error in the console log will lead to a test
failure but a test can be forced to fail with the explicit error message
in the browser console "test failed".

As a bonus, the python logger should now also log browser js trace messages.

closes odoo/odoo#31158