m/test/launch: build image at runtime

Test launch now builds the node disk image from the OCI image, instead
of creating a qcow2 snapshot of the pre-built disk image. This speeds up
tests and test cluster launch.

The OCI image is uncompressed and payloads are not verified, which
enables the previously implemented copy_file_range optimization. If the
host file system supports reflinks, this has a similar effect as the
qcow2 snapshot had previously: Building the image is very fast as the
rootfs data is not copied on disk. On my machine, it takes 30 ms.

The build before launching a cluster is now faster: The MkImage step
taking 6 s is replaced by MkOCI taking 1 s. The majority of this time is
spent by Bazel computing hashes of files. For MkImage, the generated
file was a 5 GB disk image consisting mostly of zeroes, which took a
long time to hash.

Additionally, the qcow2 layer added some overhead, which is now gone.
The HA e2e test previously took 103 s on my machine, now it takes 80 s.

Change-Id: I0ce5059626cc682061c26ac3c8d11b752e641c60
Reviewed-on: https://review.monogon.dev/c/monogon/+/4294
Tested-by: Jenkins CI
Reviewed-by: Tim Windelschmidt <tim@monogon.tech>
diff --git a/metropolis/node/BUILD.bazel b/metropolis/node/BUILD.bazel
index 60368ff..ff24cca 100644
--- a/metropolis/node/BUILD.bazel
+++ b/metropolis/node/BUILD.bazel
@@ -140,6 +140,17 @@
     visibility = ["//visibility:public"],
 )
 
+oci_os_image(
+    name = "oci_image_uncompressed",
+    srcs = {
+        "system": ":verity_rootfs",
+        "kernel.efi": ":kernel_efi",
+    },
+    compression_level = 0,
+    product_info = ":product_info",
+    visibility = ["//metropolis/test/launch:__pkg__"],
+)
+
 # An intermediary "bundle" format until we finalize the actual bundle format. This is NOT stable until migrated
 # to the actual bundle format.
 # TODO(lorenz): Replace this