Prepare releases/../app_spec for boostrap2

Prepare spec/frontend/releases/detail/components/app_spec.js specs for BootstrapVue upgrade

This MR lays the groundwork for the BootstrapVue upgrade that will be done in this MR: !18913 (merged). Due to some changes in the BTooltip and BPopover components, some related tests started failing after the upgrade. Those tests need to be updated accordingly:

• Migrate specs to use vue-test-utils
• sync needs to be set to false
• attachToDocument must be true

This MR focuses on upgrading the tests located in [spec file relative paths]:

Why are these changes necessary?

• The reason to migrate the tests to vue-test-utils is that it allows us to set the sync and attachToDocument properties.
• The reason to set attachToDocument to true is that the BTooltip and BPopover directives expect to be attached to a document object.
• The reason to set sync to false is that otherwise, specs for components that use BTooltip or BPopover will fail with the following error:

TypeError: Cannot read property 'sync' of null

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

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