Make CableTier more accessible

[Swedz]

Contains some parts of #900

It might make sense to also add the CableTierHolder interface to electric machines and get the tier from their casing component. That can easily be done. Doing it for multi blocks is a little ambiguous since a multi block electric machine can have multiple types of hatches on it. It could just use the highest tier, though. Would either of these changes be acceptable?

[Technici4n]

What is the motivation behind these changes? I.e. how are they helpful?

[Swedz]

I use it quite a bit for my tesla coil machines I've been working on for EI.

It lets me make an anonymous instance of CasingComponent to track when the casing changes and do some updates to the network when that happens.

Plus, it makes grabbing the cable tier of a tesla coil block/multiblock much more straightforward (I was previously using a mixin to do this) - and I need that to be able to wirelessly transfer power on a specific voltage.

[Technici4n]

It lets me make an anonymous instance of CasingComponent to track when the casing changes and do some updates to the network when that happens.

It would be cleaner to add an optional change notification callback IMO.

[Swedz]

I made those changes. I didn't add CableTierHolder to AbstractStorageMachineBlockEntity (and thus TransformerMachineBlockEntity) because it holds two different cable tiers and I wasn't sure which one would be best to return there.