Verify vectorized conditional expressions (if/then/else)

[onelson]

Following on from #4601.

Once the feature-flagged vectorized implementation has been released, check it out in lovelace to make sure they are working as intended.

Once satisfied, enable the feature flag for everyone, then remove the feature flag.

[onelson]

Flipped the flag on in lovelace to collect some metrics.

[onelson]

Bumping this one a few sprints down the line for flag removal.

[onelson]

Having had to turn this off (twice) for an assortment of issues (several unrelated directly to conditionals), this is back on and the logs have not shown any new defects re: vectors.

I think we're safe to leave this on and prepare to remove the flag in a couple weeks.

[onelson]

Nothing new showed up related to vectorized conditionals -- punting this to a future sprint for flag removal.