Use max z-index in Tooltip

[grotlue]

Description

Use max z-index for Tooltip as it should be visible in overlays. Added it to the component directly as it got ignored on the styles. Using a mantine z-index variable, which we should implement in other places as well to avoid these issues. Todo: Create issue for that. See https://mantine.dev/styles/css-variables/#z-index-variables.

Motivation and Context

This fixes tooltips not being visible in Modals, e.g. the Copy to Clipboard button in AI Report modal (Security/Investivations).

How Has This Been Tested?

Screenshots (if appropriate):

Types of changes

• [ ] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Refactoring (non-breaking change)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• [ ] My code follows the code style of this project.
• [ ] My change requires a change to the documentation.
• [ ] I have updated the documentation accordingly.
• [ ] I have read the CONTRIBUTING document.
• [ ] I have added tests to cover my changes.