Separate validation out of site profile creation - Create DastSiteValidationModal component

• Parent epic: &4871 (closed)

Implementation plan

• Create the DastSiteValidationModal component.
  • It replaces the DastSiteValidation component.
  • The modal should accept a targetUrl prop.
  • The modal creates a validation token for the targetUrl.
  • While the token is being created, show a skeleton loader instead of the validation form.
  • Clicking on the Validate button triggers the dastSiteValidationCreate mutation and closes the modal.
• Add tests for the DastSiteValidationModal component.
  • Skeleton loader while creating token.
  • Token create mutation.
  • Error upon token creation failure.