build(qemu): upgrade qemu from v9.2.0 to v9.4.0 and switch to base-images pm

Replace custom QEMU build pipeline with package manager-based installation.
Remove the manual install script, SCSI serial truncation patch, and
extensive configure/compile steps in favor of `pm install qemu`.

- Bump QEMU version to v9.4.0 in versions.yml and oss.yaml
- Delete install-qemu.sh and patches directory
- Simplify werf.inc.yaml to use builder/distroless with pm install
- Update virt-launcher import path from /BINS to /qemu-img

Author: flant-pinegal

build/components/versions.yml

@@ -1,5 +1,5 @@
 firmware:
-  qemu: v9.2.0
+  qemu: v9.4.0
   libvirt: v10.9.0
   edk2: stable202411
 core: