Add tool to verify host-key documents

Add a tool that can be used to verify if a given IBM host-key document is
valid. This uses the same logic (and code) as the image/request tools
for IBM Secure Execution, pvimg, pvattest, and pvsecret.

This tool basically just does the first step of the above tools; but without
creating any request or image.

Reviewed-by: Jan Höppner <hoeppner@linux.ibm.com>
Signed-off-by: Steffen Eiden <seiden@linux.ibm.com>

rust/Cargo.lock

@@ -679,6 +679,18 @@ dependencies = [
  "utils",
 ]
 
+[[package]]
+name = "pvverify"
+version = "0.12.0"
+dependencies = [
+ "anyhow",
+ "clap",
+ "clap_complete",
+ "log",
+ "s390_pv",
+ "utils",
+]
+
 [[package]]
 name = "quick-error"
 version = "1.2.3"