feat: allow set disk size & type on vm runners

[davidmontoyago]

Allow setting the disk size on modules/gh-runner-mig-container-vm and modules/gh-runner-mig-vm for thin provisioning

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[davidmontoyago]

Hi @apeabody @bharathkkb, can I get a review? the current 100gb size is too generous causing quotas to exceed when launching a handful of runners.

[apeabody]

/gcbrun

[apeabody]

/gemini review

[gemini-code-assist]

Code Review

This pull request introduces the ability to configure the disk size and type for VM runners in both gh-runner-mig-container-vm and gh-runner-mig-vm modules. The changes are well-implemented, exposing disk_size_gb and disk_type as variables and updating the documentation accordingly. My review includes suggestions to add validation blocks for these new variables to improve the robustness of the modules by ensuring that only valid values are provided during configuration.

[apeabody]

Thanks for the contribution @davidmontoyago!