Improvements: (Legacy) Select

[mrosvik]

It is decided to divide the existing Selectcomponent into multiple components:

• Autocomplete (single og multi)
• Select (group in Storybook):
  • Select (should support formating in dropdown) Could be based on Floating UI?
  • NativeSelect

This existing Select component will be renamed to Legacy Select

Related issues to Legacy select:

### List of identified improvements for our existing Select component:
- [ ] https://github.com/digdir/designsystem/issues/55
- [ ] https://github.com/digdir/designsystem/issues/66
- [ ] https://github.com/Altinn/app-frontend-react/issues/116
- [ ] https://github.com/digdir/designsystem/issues/180
- [ ] https://github.com/Altinn/altinn-design-system/issues/201
- [ ] https://github.com/digdir/designsystem/issues/270
- [ ] https://github.com/digdir/designsystem/issues/274
- [ ] https://github.com/digdir/designsystem/issues/298
- [ ] https://github.com/digdir/designsystem/issues/314
- [ ] https://github.com/digdir/designsystem/issues/307
- [ ] https://github.com/digdir/designsystem/issues/368
- [ ] https://github.com/digdir/designsystem/issues/398
- [ ] https://github.com/digdir/designsystem/issues/600
- [ ] https://github.com/digdir/designsystem/issues/607
- [ ] Select: Fix testing errors/warnings
- [ ] Select: Wrong option is read out when de-selecting by MacOs VoiceOver on Chromium
- [ ] Support for deleting selected options on `Backspace` in Select
- [ ] Support for floating dropdown on Select
- [ ] https://github.com/digdir/designsystem/issues/464

[mrosvik]

Vi har hatt et arbeidsmøte rundt Select-komponenten (i forbindelse med flere bugs som har blitt rapportert) og innser at denne komponenten skal løse veldig mye og dermed blir kompleks. Andre designsystem løser dette ofte med flere komponenter. Inntil videre skal vi supportere den eksisterende select-komponenten som er i bruk og fikse de mest kritiske bugsene på denne. Litt mer langsiktig tenker vi det kan være lurt å dele opp komponenten i mer avgrensede oppgaver:

• En Autocomplete-komponent som støtter - enkeltvalg og flervalg
• En select-komponent som støtter formatering i dropdown
• En NativeSelect

Eksisterende Select-component blir fra nå av kalt Legacy Select.