Bring back e2e tests, locally

[estellecomment]

Removed tests

• for create DM, because afaik Tchap does not have any custom code for this, so Tchap should not be maintaining these tests. The tests were broken.
• for external user login. There is nothing special about externals for login. The tests were skipped.

Other small things :

• move utils dir, it was in test dir
• fix linter in files that I edited
• remove a useless import that was obsolete (browser-request)
• fix small regression (data-test-id is now data-testid)

Tests pass locally, but not in CI.
Will deal with CI in another PR.