Add confirmation message when regenerating feature flags instance ID

What does this MR do?

This MR aims to solve the problem described in #209214 (closed) by:

• moving the Regenerate instance ID button to the bottom of the modal and default disable it
• adding a message to warn the user about the consequences of regenerating the instance ID
• adding a field for the user fo fill the project name as a verification of the intent to regenerate the instance ID

Screenshots

Idle	Verified	Loading	Cannot generate

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers
• Informed Infrastructure department of a default or new setting change, if applicable per definition of done

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• Label as security and @ mention @gitlab-com/gl-security/appsec
• The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• Security reports checked/validated by a reviewer from the AppSec team