Selenium: unexpected fail of ImportProjectFromGitHubTest selenium test

[SkorikSergey]

What does this PR do?

This PR:

• adds to ProjectSourcePage selenium page object methods for authorization on GitHub(it will fixed Unexpected fail of the ImportProjectFromGitHubTest selenium test #8226 issue);
• adds try/catch block to ImportProjectFromGitHubTest test because this test fails on OCP multiuser([OCP Multiuser] Authorization on the GitHub from dashboard does not work #8250);
• removes try/catch block from ImportProjectFromGitHubTest test because The Create button for starting a workspace doesn't work if in the Projects list selected a project imported from github #6323 is fixed.

What issues does this PR fix or reference?

#8226