testplan: Allow input protos to be binary proto or json proto.

- For the FlatConfigList input, makes a significant difference
(from > 1 minute to < 10 seconds) in time to parse.

- Allow users to pass either format as input, and just try to
parse both.

BUG=b:182898188
TEST=CQ

Change-Id: I586e64df7027bb38752cf87798ebcb981dc7852e
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/dev-util/+/3101065
Reviewed-by: Jaques Clapauch <jaquesc@google.com>
Reviewed-by: Sean McAllister <smcallis@google.com>
Commit-Queue: Andrew Lamb <andrewlamb@chromium.org>
Tested-by: Andrew Lamb <andrewlamb@chromium.org>
2 files changed