Adds E2E specs for pipeline status emails

Description of the test

This MR adds an E2E test for pipeline status emails to run in Test::Integration::SMTP scenario/job.

It utilizes the SMTP configuration to run a passing and failing pipeline on a project, and validates:

• that the correct number of emails were sent to the recipients.
• that the subject of the email includes the project name and pipeline status
• that the recipients are known

Test Cases:

1. https://gitlab.com/gitlab-org/gitlab/-/quality/test_cases/366240
2. https://gitlab.com/gitlab-org/gitlab/-/quality/test_cases/366241

Checklist

• Confirm the test has a testcase: tag linking to an existing test case in the test case project.
• Note if the test is intended to run in specific scenarios. If a scenario is new, add a link to the MR that adds the new scenario.
• Follow the end-to-end tests style guide and best practices.
• Use the appropriate RSpec metadata tag(s).
• Ensure that a created resource is removed after test execution. A Group resource can be shared between multiple tests. Do not remove it unless it has a unique path. Note that we have a cleanup job that periodically removes groups under gitlab-qa-sandbox-group.
• Ensure that no transient bugs are hidden accidentally due to the usage of waits and reloads.
• Verify the tags to ensure it runs on the desired test environments.
• If this MR has a dependency on another MR, such as a GitLab QA MR, specify the order in which the MRs should be merged.
• (If applicable) Create a follow-up issue to document the special setup necessary to run the test: ISSUE_LINK
• If the test requires an admin's personal access token, ensure that the test passes on your local environment with and without the GITLAB_QA_ADMIN_ACCESS_TOKEN provided.