tflite: add stable delegate acceleration test config file helper

This is a script mainly to help partners to generate the initial
accel_test.conf file during the bringup stage.

Additionally, this can provide us an easier way to know what tests
are supported/unsupported by a delegate.

BUG=b:332423167
TEST=run `./stable_delegate_accel_test_conf.py --stable_delegate_settings_file=sample_settings.json` on DUT

Change-Id: Ied7be511ec44bdd7e7564aa1fb719123540b60d1
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/tflite/+/5414933
Auto-Submit: Tommy Chiang <ototot@google.com>
Reviewed-by: Shik Chen <shik@chromium.org>
Tested-by: Tommy Chiang <ototot@google.com>
Commit-Queue: Tommy Chiang <ototot@google.com>