DAST creates the connection to the ZAP server

What does this MR do?

Moves the creation of the ZAP client from the ZAP Python scripts into the DAST Python scripts.

This MR includes creation of the following environment variables:

• DAST_ZAP_CONNECT_SLEEP_SECONDS: The amount of seconds to wait between each connection attempt to the ZAP API,
• DAST_ZAP_MAX_CONNECTION_ATTEMPTS: The amount of connection attempts to make to the ZAP API before aborting
• DAST_PASSIVE_SCAN_MAX_WAIT_TIME: The amount of minutes to wait for the passive scan to complete

Previously, the -T option was being used for both the "timeout" for how long to wait for a connection and the timeout for how long a passive scan should take.

What are the relevant issue numbers?

gitlab-org/gitlab#218814 (closed)

Does this MR meet the acceptance criteria?

• Changelog entry added
• Documentation created/updated for GitLab EE, if necessary
• Documentation created/updated for this project, if necessary
• Documentation reviewed by technical writer or follow-up review issue created
• Tests added for this feature/bug
• Job definition updated, if necessary
  • Job definition example
  • Vendored CI Templates (also in CE)
• Conforms to the code review guidelines
• Conforms to the Go guidelines
• Security reports checked/validated by reviewer