Use same runtime to restore a container as during checkpointing

There are at least two runtimes that support checkpoint and restore:
runc and crun. Although the checkpoints created by these are almost
compatible, it is not (yet) possible to restore a checkpoint created
with one runtime with the other runtime. To make checkpoint/restore
usage more comfortable this adds code to look into the checkpoint
archive during restore and to set the runtime to the one used during
checkpointing.

This also adds a check, if the user explicitly sets a runtime during
restore, that the runtime is also the same as used during checkpointing.

If a different runtime is selected than the one used during
checkpointing the restore will fail early.

If runc and crun will create compatible checkpoints in the future the
check can be changed to treat crun and runc as compatible
checkpoint/restore runtimes.

Signed-off-by: Adrian Reber <areber@redhat.com>

docs/source/markdown/podman-container-restore.1.md

@@ -77,6 +77,12 @@ Import a checkpoint tar.gz file, which was exported by Podman. This can be used
 to import a checkpointed *container* from another host.\
 *IMPORTANT: This OPTION does not need a container name or ID as input argument.*
 
+During the import of a checkpoint file Podman will select the same container runtime
+which was used during checkpointing. This is especially important if a specific
+(non-default) container runtime was specified during container creation. Podman will
+also abort the restore if the container runtime specified during restore does
+not much the container runtime used for container creation.
+
 #### **--import-previous**=*file*
 
 Import a pre-checkpoint tar.gz file which was exported by Podman. This option