Shell: add failsafe for irmin errors

This MR aims to mitigate the so called unknown inode key that is triggered by irmin. To do so, it catches the error thanks to a pattern match and, if found, gracefully shutdown the node.

Manually testing the MR

Apply the following diff that:

• triggers the dummy irmin error when applying a block
• adds a tests that reproduces the issue

Run with dune exec ./tezt/tests/main.exe -- wip_irmin --verbose

diff --git a/src/lib_validation/block_validation.ml b/src/lib_validation/block_validation.ml
index 1e25a60e84..937144d8a3 100644
--- a/src/lib_validation/block_validation.ml
+++ b/src/lib_validation/block_validation.ml
@@ -827,6 +827,10 @@ module Make (Proto : Protocol_plugin.T) = struct
             (Validation_errors.Inconsistent_hash
                (resulting_context_hash, block_header.shell.context))
         in
+        let () =
+          Stdlib.failwith
+            {|{"Direct":["CoWN2vbeRX7UktgiojGVpCYzjP4kse7gwSR1rLJCJryjGpcynkxi",388968996717,360]}: unknown inode key (find_value)|}
+        in
         let validation_store =
           {
             resulting_context_hash;
diff --git a/tezt/tests/baking.ml b/tezt/tests/baking.ml
index 9e8c85bf86..ac14434587 100644
--- a/tezt/tests/baking.ml
+++ b/tezt/tests/baking.ml
@@ -731,12 +731,45 @@ let baking_with_given_minimal_timestamp ~minimal_timestamp =
   in
   Client.bake_for_and_wait ~minimal_timestamp client
 
+let wip_irmin =
+  Protocol.register_test
+    ~supports:Protocol.(From_protocol (number Alpha))
+    ~__FILE__
+    ~title:"wip_irmin"
+    ~tags:["wip_irmin"]
+  @@ fun protocol ->
+  let* node1, client1 =
+    Client.init_with_node
+      ~nodes_args:[Synchronisation_threshold 0; Connections 1]
+      `Client
+      ()
+  in
+  let* node2, _client2 =
+    Client.init_with_node
+      ~nodes_args:[Synchronisation_threshold 0; Connections 1]
+      `Client
+      ()
+  in
+  let* () = Client.Admin.connect_address client1 ~peer:node2 in
+  let* () = Client.activate_protocol_and_wait ~protocol client1 in
+  let* _ = Node.wait_for_level node1 1 in
+
+  let* () = Lwt_unix.sleep 2. in
+  let* () = Client.bake_for_and_wait ~node:node1 client1 in
+
+  let* () = Lwt_unix.sleep 2. in
+  let* () = Client.bake_for_and_wait ~node:node2 client1 in
+
+  let* () = Lwt_unix.sleep 2. in
+  unit
+
 let register ~protocols =
   test_ordering protocols ;
   wrong_branch_operation_dismissal protocols ;
   baking_operation_exception protocols ;
   baking_with_given_minimal_timestamp ~minimal_timestamp:false protocols ;
-  baking_with_given_minimal_timestamp ~minimal_timestamp:true protocols
+  baking_with_given_minimal_timestamp ~minimal_timestamp:true protocols ;
+  wip_irmin protocols
 
 let register_operations_pool ~protocols =
   List.iter

Checklist

• Document the interface of any function added or modified (see the coding guidelines)
• Document any change to the user interface, including configuration parameters (see node configuration)
• Provide automatic testing (see the testing guide).
• For new features and bug fixes, add an item in the appropriate changelog (docs/protocols/alpha.rst for the protocol and the environment, CHANGES.rst at the root of the repository for everything else).
• Select suitable reviewers using the Reviewers field below.
• Select as Assignee the next person who should take action on that MR