Fix GitLab runner snippets to run as current user on Windows and Mac

Problem

As per https://github.com/redhat-developer/mapt/pull/711, more specifically GitLab runner snippets for Windows and Mac install as system services running under privileged accounts (SYSTEM/root), unlike other integrations (GitHub Actions, Cirrus) which run as the current user.

See related comment in PR: https://github.com/redhat-developer/mapt/pull/711#issuecomment-3785957041

Impact

• Permissions issues accessing user files/directories
• Different behavior than other CI runner integrations
• Security concerns running as elevated accounts

Solution

Update snippets to match pattern from GitHub/Cirrus integrations:

Mac (snippet-darwin.sh)

• Configure LaunchDaemon UserName to run as current user
• Similar to: pkg/integrations/github/snippet-darwin.sh line 10 or pkg/integrations/cirrus/snippet-darwin.sh lines 32-35

Windows (snippet-windows.ps1)

• Either use startup folder approach (like Cirrus)
• Or configure service to run as current user

Files

• pkg/integrations/gitlab/snippet-darwin.sh
• pkg/integrations/gitlab/snippet-windows.ps1

Reference

• GitHub snippet: pkg/integrations/github/snippet-darwin.sh
• Cirrus snippet: pkg/integrations/cirrus/snippet-darwin.sh

Start with pkg/integrations/gitlab/snippet-darwin.sh and pkg/integrations/gitlab/snippet-windows.ps1, then compare them with the referenced GitHub and Cirrus snippets. Verify the macOS LaunchDaemon and Windows runner setup use the current user without elevated-account permission problems, while preserving the existing GitLab runner behavior.