Simplify test&save actions when setting a service integration

What does this MR do?

It changes how integrations are tested and updated.

When a service is not checked as active on edit page a user can save the result but sees the message that the service was not activated.

When a service is checked as active and all required fields are filled in (required fields are defined on service classes) the service settings are tested (if a service supports this). If the test fails an error message is displayed but a user can still save the settings. If the test succeeds the service is saved and activated immediately.

For more information see the related issue.

Are there points in the code the reviewer needs to double check?

The changes were targeted mostly for JIRA but also other services were affected.

Why was this MR needed?

We want to simplify JIRA service settings. JIRA uses the general workflow for setting services so we are changing this general workflow and will simplify it for all integrations.

Screenshots (if relevant)

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• API support added
• Tests
  • Added for this feature/bug
  • All builds are passing
• Conform by the merge request performance guides
• Conform by the style guides
• Branch has no merge conflicts with master (if it does - rebase it please)
• Squashed related commits together

What are the relevant issue numbers?

Closes #31511 (closed)