Remove numbers from alerts integration settings

What does this MR do and why?

The Alerts project settings shows fields prepended with numbers.

The numbers are unnecessary, because:

• You have to select the integration type to reveal other fields.
• Optional fields are already marked as optional.

Also, add select ID for label to fix a11y issue.

References

Remove numbered steps from Monitor > Alerts set... (#383688 - closed)

MR acceptance checklist

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Screenshots or screen recordings

Before	After

How to set up and validate locally

You must have at least the Maintainer role for the project.

1. On the left sidebar, select Search or go to and find your project.
2. Select Settings > Monitor.
3. Expand Alerts.
4. Select Add new integration.
5. From the dropdown, select any integration type. You should now see all the fields.