Align support/geo-install with support/install

What does this merge request do and why?

As concluded in the discussion thread of !5403 (closed), geo-install is a "golden path" installation script that enforces mise for tool version management, similar to the install script. Therefore, we can safely use mise exec -- directly instead of the tool-version-manager-exec wrapper.

This change:

• Replaces all ./support/tool-version-manager-exec calls with mise exec -- in support/geo-install
• Adds asdf.opt_out: true in setup_tool_version_manager(), like support/install
• Fixes the community fork URL

Related to !5403 (closed)

Impacted categories

• gdk-usability - Simplifies the geo-install script by using mise directly

Merge request checklist

• This change is backward compatible.
• [-] Tests added for new functionality. If not, raise an issue to follow-up.
• [-] Documentation added/updated.