E2E tests for 2FA recovery via SSH

What does this MR do?

• Adds a new e2e test for 2FA recovery via SSH
• Moves ssh related code from qa/qa/git/repository.rb into its own file qa/qa/lib/ssh.rb
• Moves command run related code from qa/qa/git/repository.rb into its own file qa/qa/support/run.rb
• Adds specs for qa/qa/support/run.rb and qa/qa/support/run.rb

Closes gitlab-org/quality/testcases#966 (closed) and #208873 (closed)

Screenshots

Does this MR meet the acceptance criteria?

Conformity

• [-] Changelog entry
• [-] Documentation (if required)
• Code review guidelines
• [-] Merge request performance guidelines
• Style guides
• [-] Database guides
• [-] Separation of EE specific content

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• [-] Label as security and @ mention @gitlab-com/gl-security/appsec
• [-] The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• [-] Security reports checked/validated by a reviewer from the AppSec team