Error tracking settings - add project selection dropdown

What does this MR do?

Adds the frontend for the Error Tracking Settings page Sentry project selection

Before	After

New states

Initial	Connected	Dropdown open

Project Selected	Connection Error	Invalid project

What are the relevant issue numbers?

#55199 (closed)

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated via this MR
• Documentation reviewed by technical writer or follow-up review issue created Follow up MR here https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/24924
• Tests added for this feature/bug
• Tested in all supported browsers
• Conforms to the code review guidelines
• Conforms to the merge request performance guidelines
• Conforms to the style guides
• Conforms to the database guides
• Link to e2e tests MR added if this MR has Requires e2e tests label. See the Test Planning Process.
• Security reports checked/validated by reviewer

Before merging

• Add .pot file changes to EE backport MR (https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/9400)
• Merge the EE backport MR (https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/9400)
• Wait for the backend MRs to be ready: https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/24681 https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/24700 https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/24701
• Frontend Review
• UX Review