Revert "update_engine: Deprecate major version 1"

This partially reverts commit 55c75417e22d5026971276997924a345d9973bbc.

It turns out that we forgot a scenario when we deprecated major version
1. We use update_engine in lab tests (specifically
autoupdate_EndToEndTests on stable channel) to update a DUT to an
old (very old) versions using actual update payloads so we can test that
they can get updated to newer versions. However, deprecating major
version 1 in the update_engine caused trouble because we no longer can
update from a newer version to a version before M72 (to prepare the
device for update test). We need to put this feature back until we find
a better solution for it.

On this CL, we only support major version 1 in the client and only for
test (non-official) images. We don't even bother adding paygen support
for it.

This CL should be reverted once we figured out what to do with
provisioning the autoupdate end to end tests.

BUG=chromium:1043428
TEST=FEATURES=test emerge-reef update_engine
TEST=cros deployed it, then cros flash using an m71 payload, it succeeded.

Change-Id: I1fecbe3ae845b2e419f0999adc53e4732b1f7696
Reviewed-on: https://chromium-review.googlesource.com/c/aosp/platform/system/update_engine/+/2013884
Reviewed-by: Tianjie Xu <xunchang@google.com>
Reviewed-by: Sen Jiang <senj@chromium.org>
Tested-by: Amin Hassani <ahassani@chromium.org>
Commit-Queue: Amin Hassani <ahassani@chromium.org>
diff --git a/payload_generator/payload_signer.cc b/payload_generator/payload_signer.cc
index 420329f..613202d 100644
--- a/payload_generator/payload_signer.cc
+++ b/payload_generator/payload_signer.cc
@@ -94,7 +94,7 @@
   brillo::Blob payload;
   TEST_AND_RETURN_FALSE(utils::ReadFile(payload_path, &payload));
   PayloadMetadata payload_metadata;
-  TEST_AND_RETURN_FALSE(payload_metadata.ParsePayloadHeader(payload));
+  TEST_AND_RETURN_FALSE(payload_metadata.ParsePayloadHeader(payload, nullptr));
   uint64_t metadata_size = payload_metadata.GetMetadataSize();
   uint32_t metadata_signature_size =
       payload_metadata.GetMetadataSignatureSize();
@@ -218,7 +218,7 @@
   brillo::Blob payload;
   TEST_AND_RETURN_FALSE(utils::ReadFile(payload_path, &payload));
   PayloadMetadata payload_metadata;
-  TEST_AND_RETURN_FALSE(payload_metadata.ParsePayloadHeader(payload));
+  TEST_AND_RETURN_FALSE(payload_metadata.ParsePayloadHeader(payload, nullptr));
   DeltaArchiveManifest manifest;
   TEST_AND_RETURN_FALSE(payload_metadata.GetManifest(payload, &manifest));
   TEST_AND_RETURN_FALSE(manifest.has_signatures_offset() &&