build_report: Add payload information

Several fields from the JSON mentioned in b/213383473 are
covered by existing fields in the BuildArtifact message:
- payload URI
- full or delta (i.e. "is_delta")
- sha256 hash (not sure if it is hex)

BUG=b:213383473
TEST=./generate.sh

Change-Id: I892e8e4a29f61e6b123c23df7f934523ce6cea6d
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/infra/proto/+/3437606
Reviewed-by: Benjamin Shai <bshai@google.com>
Reviewed-by: George Engelbrecht <engeg@google.com>
Reviewed-by: Arthur Bello <artbello@google.com>
Commit-Queue: Jack Neus <jackneus@google.com>
3 files changed