treewide: port everything to blockdev

This gets rid of most ad-hoc block device code, using blockdev for
everything. It also gets rid of diskfs for everything but tests. This
enables Metropolis to be installed on non-512-byte block sizes.

Change-Id: I644b5b68bb7bed8106585df3179674789031687a
Reviewed-on: https://review.monogon.dev/c/monogon/+/1873
Tested-by: Jenkins CI
Reviewed-by: Serge Bazanski <serge@monogon.tech>
diff --git a/cloud/agent/BUILD.bazel b/cloud/agent/BUILD.bazel
index e8b4ffd..793f15b 100644
--- a/cloud/agent/BUILD.bazel
+++ b/cloud/agent/BUILD.bazel
@@ -18,6 +18,7 @@
         "//metropolis/node/build/mkimage/osimage",
         "//metropolis/node/core/devmgr",
         "//metropolis/node/core/network",
+        "//metropolis/pkg/blockdev",
         "//metropolis/pkg/bootparam",
         "//metropolis/pkg/efivarfs",
         "//metropolis/pkg/logtree",