[YANGTOOLS-1397] Expose a knob to control warnings about unkeyed lists with config=true

Issue split — Fri, 22 Apr 2022 16:31:46 +0000

We are warning about lists with config=true without a key, which is on par with RFC7950. We use such lists internally quite extensively, which results in not-so-nice startup.
Add a YangParserConfiguration knob to control this output, default to false and let CLI tools enable it.

A follow-up patch will then disable them by default in the next major release.

OpenDaylight JIRA

[YANGTOOLS-1397] Expose a knob to control warnings about unkeyed lists with config=true