[react@18] fix field.helpText type issue

[Dosant]

Summary

Part of #138222

This is one of the issues that @types/react@18 upgrade highlights and that needs to be addressed with or before the upgrade.

field.helpText is ReactNode, a function is not a valid ReactNode, but @types/react@17 allowed a function. That is why typeof field.helpText === 'function' ? field.helpText() : field.helpText doesn't fail with @17, but fails with @18 as field.helpText is not callable, as never is not callable. You can check the types with @types/react@18 yourself here #191738

It looks like the lazy helpText isn't needed apart from a hack for index management where documentation service is used as part of helpText that could be not available yet.

To keep it supported, I specifically, allowed a function that returns a ReactNode for helpText on FieldConfig, but to make consumption clean and to now break other places useField will call it and pass just a ReactNode down

[Dosant]

Here we allow a lazy helpText. It is already used like this in some places, it worked because a function could be assigned to ReactNode due to a mistake in @types/react@17. This is no longer allowed with @types/react@18

[Dosant]

Here we're unwraping the lazy helpText so that the useField() receives the ReactNode value. This allows to simplify a bunch of existing places and not to fix a bunch of other places where helpText={helpText} is already used

[kibana-ci]

💛 Build succeeded, but was flaky

• Buildkite Build
• Commit: 0760701

Failed CI Steps

Metrics [docs]

Async chunks

Total size of all lazy-loaded chunks that will be downloaded as the user navigates the app

id	before	after	diff
dataViewEditor	49.4KB	49.3KB	-43.0B
indexManagement	679.7KB	679.6KB	-43.0B
total			-86.0B

Page load bundle

Size of the bundles that are downloaded on every page load. Target size is below 100kb

id	before	after	diff
esUiShared	158.9KB	158.2KB	-706.0B
triggersActionsUi	121.7KB	121.6KB	-43.0B
total			-749.0B

To update your PR or re-run it, just comment with:
@elasticmachine merge upstream

[elasticmachine]

Pinging @elastic/appex-sharedux (Team:SharedUX)

[davismcphee]

Code-only review, Data Discovery changes LGTM 👍

[cnasikas]

ResponseOps changes LTGM!

[ElenaStoeva]

Index Management changes lgtm!