camera: prepare CAMX overlay runtime for NHX validation

[Srikanth Muppandam (smuppand)]

Summary

Improve Camera_NHX setup and runtime validation on Debian CAMX systems, including Glymur.

Changes

• Discover nhx.sh from PATH or /usr/libexec/camx/nhx.sh.
• Recognize Glymur/X1E and select camera_x1e80100.
• Detect CAMX packages through opkg, dpkg-query, DNF, or RPM.
• Continue after successful --overlay package-set verification if package inventory is unavailable.
• Make camx the required FIT DTB selection for --overlay.
• Discover VendorDtbOverlays dynamically instead of hardcoding its GUID.
• Verify the EFI value using efivar -p.
• Write and read back camx, then synchronize storage when selection is required.
• Never reboot automatically.
• Report SKIP with a manual-reboot instruction after changing the EFI selection.
• Report manual reboot required when EFI selects camx but the board-specific camera module is not loaded.
• Confirm runtime CAMX readiness when the expected camera module is loaded.

Result behavior

• SKIP when the CAMX FIT DTB was selected for the next boot and a manual reboot is required.
• SKIP when EFI selects camx but the expected camera module is not loaded.
• FAIL when the EFI selection cannot be written or verified.
• Continue with NHX validation only after EFI selection and runtime camera-module readiness are confirmed.

Fixes #595