feat: vmtest.sh: the boot loader test for every loader the ISO advertises

One VM per loader, Steam Machine (--fremont): Steamify's state as its menu sees it,
OS name untouched, loader identity, the DKMS modules for every kernel, Steamify's
loader-specific code (hdmi_remove_boot_param), a kernel update, and a reboot into
each of the two kernels. Headless by default with a log Konsole (--window shows
the VMs). Fails when an advertised loader has no test. Limine 41, systemd-boot 40,
GRUB 40 checks pass.

share/bootloader-test/modules.sh

@@ -0,0 +1,15 @@
+#!/bin/bash
+# Guest side: Steamify's DKMS modules exist for every installed kernel.
+# Prints PASS/FAIL lines (scripts/vmbootloadertest.sh counts the FAILs).
+pass() { echo "PASS $*"; }; fail() { echo "FAIL $*"; }
+kernels=$(ls /usr/lib/modules)
+n=$(wc -w <<< "$kernels")
+echo "kernels: $(tr '\n' ' ' <<< "$kernels")"
+dkms status
+[[ $(dkms status | grep -c ': installed') -eq $((3 * n)) ]] && pass "3 DKMS modules x $n kernels installed" || fail "dkms status is not 3 modules x $n kernels"
+for k in $kernels; do
+    for m in cros-ec-cec leds-valve steamify-fremont-poweroff; do
+        compgen -G "/usr/lib/modules/$k/updates/dkms/$m.ko*" >/dev/null && pass "$m for $k" || fail "$m missing for $k"
+    done
+done
+[[ -f /etc/modules-load.d/steamify-fremont-poweroff.conf ]] && pass "modules-load.d has the power-off fix" || fail "no modules-load.d entry"