Add section-start and section-end delimiters for powershell
What does this MR do?
It improves gitlab-runner such that when generating commands for powershell to execute, section-start and section-end are used to mark job script sections, which allows the command output to be collapsed in the job log UI.
Why was this MR needed?
Previously, the job script output was not annotated with the section block markers, so command output was not collapsible.
What's the best way to test this MR?
Run it with different script content on various powershell/pwsh runners. I've tested macos-pwsh, windows-pwsh and windows-powershell-5, windows-docker-pwsh and windows-docker-powershell-5; they all work ok. k8s-windows-pwsh and k8s-windows-powershell-5 only work if you set FF_USE_LEGACY_KUBERNETES_EXECUTION_STRATEGY.