update_engine: Deprecate major version 1

We have moved away from major version 1 in Chrome OS and already have a
stepping stone for it in M53. So this cleanup makes the code much easier
to understand.

BUG=chromium:1008553
TEST=FEATURES="test" sudo emerge update_engine update_payload
TEST=cros_generate_update_payload --image chromiumos_test_image.bin --check --output delta.bin

Change-Id: I01815dfa5fdf395f8214ef162e01ecca2d42f7fc
Reviewed-on: https://chromium-review.googlesource.com/c/aosp/platform/system/update_engine/+/1857459
Tested-by: Amin Hassani <ahassani@chromium.org>
Reviewed-by: Sen Jiang <senj@chromium.org>
Commit-Queue: Amin Hassani <ahassani@chromium.org>
diff --git a/update_metadata.proto b/update_metadata.proto
index 3382f84..40db678 100644
--- a/update_metadata.proto
+++ b/update_metadata.proto
@@ -303,8 +303,8 @@
   // Only present in major version = 1. List of install operations for the
   // kernel and rootfs partitions. For major version = 2 see the |partitions|
   // field.
-  repeated InstallOperation install_operations = 1;
-  repeated InstallOperation kernel_install_operations = 2;
+  repeated InstallOperation install_operations = 1 [deprecated = true];
+  repeated InstallOperation kernel_install_operations = 2 [deprecated = true];
 
   // (At time of writing) usually 4096
   optional uint32 block_size = 3 [default = 4096];
@@ -319,10 +319,10 @@
 
   // Only present in major version = 1. Partition metadata used to validate the
   // update. For major version = 2 see the |partitions| field.
-  optional PartitionInfo old_kernel_info = 6;
-  optional PartitionInfo new_kernel_info = 7;
-  optional PartitionInfo old_rootfs_info = 8;
-  optional PartitionInfo new_rootfs_info = 9;
+  optional PartitionInfo old_kernel_info = 6 [deprecated = true];
+  optional PartitionInfo new_kernel_info = 7 [deprecated = true];
+  optional PartitionInfo old_rootfs_info = 8 [deprecated = true];
+  optional PartitionInfo new_rootfs_info = 9 [deprecated = true];
 
   // old_image_info will only be present for delta images.
   optional ImageInfo old_image_info = 10;