feat: implement WSL2 native mount support via path translation and boot-time bind mounting

[Nachiket-Roy]

Summary

This PR implements Phase 2 of #5152 by bringing the WSL2 driver in line with Lima's standard mount behavior.

Previously, WSL2 relied solely on its native automounts (C:\ - > /mnt/c) and ignored Lima's mounts configuration (mountPoint, writable, and per-mount location). As a result, templates behaved differently on WSL2 compared to other drivers (QEMU/VZ), with no support for custom mount points or read-only mounts.

Changes

• Added Windows -> WSL path translation (TranslateWindowsToWSLPath) for default mount point resolution.
• Improved defaults and validation to gracefully reject unsupported paths (e.g. UNC paths) instead of panicking.
• Extended cidata to pass mount location and writable metadata into the guest.
• Added a WSL2 boot-time provisioning script that:
  • creates bind mounts for custom mount points,
  • enforces writable: false via read-only bind mounts,
  • falls back to symlinks when bind mounts cannot be created,
  • safely updates /etc/wsl.conf to enable automount metadata support.
• Added unit tests and manually verified:
  • custom mount points,
  • read-only mounts,
  • idempotent reboots,
  • safe /etc/wsl.conf updates,
  • graceful validation errors for unsupported UNC paths.