[Datepicker] Bumped react-day-picker to v9.

[KenAJoh]

Description

As a result users will now not get peer-dependency warnings when running npm install since rdp v9 has react: ">= 16.8.0" set

While the upgrade-guide doesn't look that bad: https://daypicker.dev/upgrading, this major-update came with a bunch of small undocumented changes and gotchas 😭 In the end it turned into a refactor of most of our Datepicker and MonthPicker-code. While it looks like a lot has been done, most of the touched files are just small refactors like renaming and re-structuring.

Steps taken to ensure backwards compat and no breaking changes

• Set up tests in old DatePicker/MonthPicker code that ensures same output between the versions
• Storybook-tests that validates that DOM-structure matches old structure for HTML-structure, classNames and a11y-tags on elements. UX should be 1-1 🤞

Highlights

• DateWrapper -> DateDialog: Modal now has placement="top" to avoid layout-shifts with fixedWeeks set
• DateInput: Context co-located with code
• Locale -> Date.locale: Context co-located with code
• All /context-dir code is now co-located and use our own createContext-util where possible
• Because of this bug, we use the new util clamp-dates to make sure shown month/year is never "outside" the possible view.
• Moved /utils -> /date-utils for clarity
• Added new stories in DatePicker.test.stories.tsx and MonthPicker.test.stories.tsx for testing code while refactoring.
• Re-written all our "custom"-components used in rdp. The major updated how all of these worked so needed to be built from scratch. Notice that they now have useCallback when used to avoid re-renders.
• Extracted the ReactDayPicker component itself to be re-used between standalone and dialog-version
• In an effort to slowly migrate away from react-day-picker, some utilities have been extracted
• • Typeutils
• • dropdown-options

MonthPicker

Component could no longer use old utilities from rdp. We didn't use it for much before anyways, so features were extracted and replicated locally.

Component Checklist 📝

• JSDoc
• Examples
• Documentation / Decision Records
• Storybook
• Style mappings (@navikt/core/css/config/_mappings.js)
• Component tokens (@navikt/core/css/tokens.json)
• CSS class deprecations (@navikt/aksel-stylelint/src/deprecations.ts)
• Exports (@navikt/core/react/src/index.ts and @navikt/core/react/package.json)
• New component? CSS import (@navikt/core/css/index.css)
• Breaking change? Update migration guide. Consider codemod.
• Changeset (Format: <Component>: <gitmoji?> <Text>. E.g. "Button: ✨ Add feature xyz.")

[changeset-bot]

🦋 Changeset detected

Latest commit: a5c33f5

The changes in this PR will be included in the next version bump.

Not sure what this means? Click here to learn what changesets are.

Click here if you're a maintainer who wants to add another changeset to this PR

[github-actions]

Storybook demo / Chromatic

📝 Changes to review: 1

3918aeaa8 | 91 components | 135 stories

[gpbl]

Thanks for pinging your PR and the feedback here. I don’t often get the chance to see how the react-day-picker is used in real-world scenarios 👀

Sorry to hear that upgrading to DayPicker 9 has been such a difficult task. If you have a moment, please share your main pain points with other devs and maintainers. That would be a huge help!