Deprecate some replaced metadata methods and improve metadata API

[rschili]

I replaced some callers with the new calls, and ignored the deprecation warning on others. Eventually we will want to replace them all.

Deprecated methods/types
Common package:

• EntityClassMetadata
• EntityClassMetadataProps
• CustomAttribute
• PropertyMetaData
• PropertyMetaDataProps

Backend package

• Element.getClassMetaData()
• Entity.forEachProperty()
• IModelDb.classMetaDataRegistry
• IModelDb.getMetaData
• IModelDb.tryGetMetaData
• IModelDb.forEachMetaData()
• MetaDataRegistry

Also made the following (breaking) changes to ecschema-metadata:

• getSchemaItems and getProperties now always consistenty return Iterable. Before they returned IterableIterator or Arrays inconsistently.
• getProperties had a "clearCache" flag, that is gone. Cache is now implicitly cleared for the local class. For changes to the base classes, an internal "cleanCache" method has been added.
• .properties on Class is gone. It returned local properties or undefined. getProperties now takes an optional boolean flag which makes it return only local properties.

See Nextversion.md for a more comprehensive list of changes.
There are several new shortcuts and helper method that make transitioning easier.

Parent: https://github.com/iTwin/itwinjs-backlog/issues/1156
Part of: https://github.com/iTwin/itwinjs-backlog/issues/1415

[grigasp]

I don't want to have eslint-disable-next-line @typescript-eslint/no-deprecated in our owned code. I'll try to find some time to update it this week.

[rschili]

@grigasp

I don't want to have eslint-disable-next-line @typescript-eslint/no-deprecated in our owned code. I'll try to find some time to update it this week.

Hey, that's a fair point. I want to improve the messages on those deprecation warnings to point to the replacement. But I realized that our replacements are much more verbose which I don't like. I will do a follow up story to provide better drop-in replacements, shortcuts, or make other API improvements to ease the transition.
So for now I suggest we keep those deprecation ignores. It will probably be easier to switch in one or two weeks. Of course I won't keep you from doing it if you still prefer

[grigasp]

reviewed changes under presentation dir & NextVersion.md.

[christophermlawson]

Looks good. Just that one typo.

[mergify]

This pull request is now in conflicts. Could you fix it @rschili? 🙏
To fixup this pull request, you can check out it locally. See documentation: https://help.github.com/articles/checking-out-pull-requests-locally/

[rschili]

Hey @aruniverse @hl662 @christophermlawson could you give this another look?
There is one open comment by Nam about the new API being public. We will want to mark it stable for one release, but we cannot wait until that mechanism becomes available.
I can change them to beta if that's preferred, I don't think it makes a real difference. The APIs used under the hood are well tested and stable.

Thanks

[mergify]

This pull request is now in conflicts. Could you fix it @rschili? 🙏
To fixup this pull request, you can check out it locally. See documentation: https://help.github.com/articles/checking-out-pull-requests-locally/