Show disabled suggestion button with tooltip message

Issue: #30707 (closed)

What does this MR do?

When a suggestion is not "appliable", the suggestion button just doesn't exist. In this MR, the suggestion button will appear but at a disabled state with a tooltip message telling that user that the suggestion can not be applied.

Testing Case

Find a merge request with code changes.

1. Go to Merge Requests > "Changes" tab
2. Comment on a line with code and click "insert suggestion" (docs)
3. Don't make any changes to the suggestion and click the "Add comment now" button

• The "Apply suggestion" should be at a disabled state
• There is a tooltip message

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

Closes #30707 (closed)