Add integrated setting to error tracking

What does this MR do?

Adds radio button for project error tracking setting. Allows user to choose a backend for error tracking.

Part of new feature: Integrated error tracking #329596 (closed)

Before this change, users need to use API to change value of integrated attribute. See https://docs.gitlab.com/ee/operations/error_tracking.html#integrated-error-tracking

Issue #329596 (closed)

Screenshots or Screencasts (strongly suggested)

Before

Only Sentry backend was supported

After

When GitLab is selected, we hide all other settings, since those are Sentry-releated.

When Sentry option is selected, we show all those integration fields.

Does this MR meet the acceptance criteria?

Conformity

• I have included changelog trailers, or none are needed. (Does this MR need a changelog?)
• I have added/updated documentation, or it's not needed. (Is documentation required?)
  • Coming in a follow-up MR
• I have properly separated EE content from FOSS, or this MR is FOSS only. (Where should EE code go?)
• [-] I have added information for database reviewers in the MR description, or it's not needed. (Does this MR have database related changes?)
• I have self-reviewed this MR per code review guidelines.
• This MR does not harm performance, or I have asked a reviewer to help assess the performance impact. (Merge request performance guidelines)
• I have followed the style guides.
• This change is backwards compatible across updates, or this does not apply.

Availability and Testing

• I have added/updated tests following the Testing Guide, or it's not needed. (Consider all test levels. See the Test Planning Process.)
• I have tested this MR in all supported browsers, or it's not needed.
• I have informed the Infrastructure department of a default or new setting change per definition of done, or it's not needed.