Ledger API: add buf checks [KVL-1045] (#10625)

CHANGELOG_BEGIN
CHANGELOG_END

buf.lock

@@ -0,0 +1,10 @@
+# Generated by buf. DO NOT EDIT.
+version: v1
+deps:
+  - remote: buf.build
+    owner: googleapis
+    repository: googleapis
+    branch: main
+    commit: d6ee4a74dbb44a97a6aa716ba9db6561
+    digest: b1-nEcyshfgfxdTLEh0TeD6dvzl3RLGkrTTm0BSTs6J6mc=
+    create_time: 2021-08-19T15:05:56.101677Z

buf.yaml

@@ -2,12 +2,17 @@
 # SPDX-License-Identifier: Apache-2.0
 
 version: v1beta1
+
+deps:
+   - buf.build/googleapis/googleapis
+
 build:
   roots:
     - daml-lf/archive/src/main/protobuf/
     - daml-lf/transaction/src/main/protobuf/
     - ledger/ledger-configuration/protobuf/
     - ledger/participant-state/kvutils/src/main/protobuf/
+    - ledger-api/grpc-definitions
   excludes:
     # We have to exclude these to avoid duplicate definitions of e.g. Unit within the same package.
     - daml-lf/archive/src/main/protobuf/com/daml/daml_lf_1_11/