metrics-ipmi-blobs: Convert to nanopb

Tested: Decoded a metric proto from a host and verified that the fields
all looked as expected and "normal" with decode successfully identifying
everything.

Change-Id: Iaa1b5500db6d1b93fae95d44a1045a858624cc51
Signed-off-by: William A. Kennington III <wak@google.com>
diff --git a/subprojects/nanopb.wrap b/subprojects/nanopb.wrap
new file mode 100644
index 0000000..cb50ef5
--- /dev/null
+++ b/subprojects/nanopb.wrap
@@ -0,0 +1,3 @@
+[wrap-git]
+url = https://github.com/nanopb/nanopb
+revision = HEAD