Add existsStatistic with Material and EntityType check

[petomka]

When I was trying to modify some statistics in batch, I noticed that there wasn't a way to check if a certain statistic and material/entity type combination exists, instead the methods just threw exceptions whenever a certain combination was invalid.

[MiniDigger]

Rename 0389-Add-existsStatistic-with-Material-and-EntityType-che.patch to 0389-Add-existsStatistic-with-Material-and-EntityType-check.patch :)

patch file names are automatically generated based off of the commit and have a length limit

[qixils]

I don't think this should be merged. I don't want to expand on this API, I want it replaced (See the existing Better Stats API PR).

The current stats API is just bad. its really that simple. No use expanding on a bad system.

it's easy to say "we should just use the new API" but considering that new API has been in PR hell for over a year now, i don't really see a good reason why not to merge this 🤷🏻‍♀️ this is a relatively minor and harmless PR; it just needs some cleaning up of the imports and some nullability annotations

[electronicboy]

slapped an approval on the other PR, I'd forgotten I'd already given it a look over as for this one,

1. maintaining extra API which is just deprecated on day 1 is pretty bleh, so not sure about that entirely
2. if this was to be merged, that API method needs to be renamed
3. needs cleanup

[Owen1212055]

Thank you for your contribution, however, as stated by Cat and Machine it's probably better to freeze any additions to this API due to its planned replacement.

I also agree with this, because this is just annoying maintenance for us on something we want to be replaced anyways.