[items] ItemHistory: Adjust to breaking changes & Add new methods for future states

[florian-h05]

Refs openhab/openhab-core#3736.

• Rename Item::history to Item::persistence.
• Rename HistoricItem to PersistedItem and introduce PersistedState for state as string, Quantity & number.
• Make variance, deviation, average, sum & delta return the state as PersistedState instead of number.
• Add **Until methods for all existing queries.
• Add nextState and nextUpdate methods.
• Rename historicState method to persistedState.
• Remove latestState method.
• Remove deprecated evolutionRate method.
• Add removeAllStatesSince, removeAllStatesUntil & removeAllStatesBetween methods.

With this PR, support for accessing persistence on openHAB 4.1.x or older will be dropped with the next openhab-js release.
Users should either upgrade openHAB to 4.2.x or stay with the current 4.x.x series of openhab-js.
Since there are no known issues in openhab-js, staying on 4.x.x should be fine.

[florian-h05]

TBD after merge:

• Update Blockly code generation.
• Update openhab-js tern defs.

[rkoshak]

Make variance, deviation, average, sum & delta return the state (including unit) as string instead of a number.

For consistency, does it make sense to offer numberAverage and quantityAverage (et. al.) same as we have in Item for accessing the state? HistoricState already has those options too so it feels reasonable to expect there to be options for these persistence queries too.

[jlaur]

• Make variance, deviation, average, sum & delta return the state (including unit) as string instead of a number.

Would it make sense to return a Quantity instead of a number? I guess in most cases the returned string would be used for creating a Quantity?

[jlaur]

I wanted to ask this question for some hours, but didn't find time until now, and just after posting I saw @rkoshak's similar question. 😄

[rkoshak]

Would it make sense to return a Quantity instead of a number?

I don't think we'd want to always return a Quantity. If the Item is a plain Number Item there is no unit so a Quantity wouldn't be appropriate in that case.

Returning a String by default with options for numeric and quantity maps to other places in the library where a state of an Item is accessed (from the Item or from a HisotricState).

[florian-h05]

My proposal is to create a class PersistedState or HistoricState inside the helper library, which has the same properties as https://openhab.github.io/openhab-js/items.HistoricItem.html but obviously without timestamp, and have the current HistoricItem just extend this class.
This way it is easily possible to get the state in different formats.

WDYT?

[rkoshak]

Works for me.

[florian-h05]

Implemented and tested 👍