Add optional Lit debug mode configuration option

Mostly just archiving this for later, I found this helpful in pinpointing what exactly was happening with Lit internals while working with FUI code that was conflicting:

window.emitLitDebugLogEvents = true;
window.addEventListener("lit-debug", (event) => {
  console.debug("Lit event:", event.detail);
});

In my case, when one of my LitElement properties was being updated, Lit was throwing an exception because the element changed outside control of Lit. I had to use debug output to figure out which property that was, and after that it was very easy to understand the conflict.

Be warned that this is a firehose of information though. I didn't want to add this under the existing debug flag because of how noisy it is.

No file or test is named. Start by locating the existing debug flag and the Lit integration, then review the issue's window.emitLitDebugLogEvents and lit-debug event example. Done means an optional configuration enables Lit debug logging without enabling the noisy output by default.