Clean up create collection view model and fragment

[NotWoods]

Second attempt at #4274

• CreateCollectionViewModel now just has state as a property, with setter functions. Long-term this logic could be moved into the store.
• SaveCollectionStep is an enum. Code using the step has been simplified.

Pull Request checklist

• Quality: This PR builds and passes detekt/ktlint checks (A pre-push hook is recommended)
• Tests: This PR includes thorough tests or an explanation of why it does not
• Changelog: This PR includes a changelog entry or does not need one
• Accessibility: The code in this PR follows accessibility best practices or does not include any user facing features

[codecov-io]

Codecov Report

Merging #4731 into master will increase coverage by 0.25%.
The diff coverage is 27.17%.

@@             Coverage Diff             @@
##             master   #4731      +/-   ##
===========================================
+ Coverage      6.53%   6.79%   +0.25%     
- Complexity      151     160       +9     
===========================================
  Files           207     207              
  Lines          9029    8997      -32     
  Branches       1359    1346      -13     
===========================================
+ Hits            590     611      +21     
+ Misses         8394    8341      -53     
  Partials         45      45

Impacted Files	Coverage Δ	Complexity Δ
...c/main/java/org/mozilla/fenix/home/HomeFragment.kt	0% <0%> (ø)	0 <0> (ø)	⬇️
...illa/fenix/collections/CollectionCreationUIView.kt	0% <0%> (ø)	0 <0> (ø)	⬇️
...lla/fenix/collections/SaveCollectionListAdapter.kt	0% <0%> (ø)	0 <0> (ø)	⬇️
...illa/fenix/collections/CreateCollectionFragment.kt	0% <0%> (ø)	0 <0> (ø)	⬇️
...ix/collections/CollectionCreationTabListAdapter.kt	0% <0%> (ø)	0 <0> (ø)	⬇️
...a/fenix/collections/CollectionCreationComponent.kt	12.76% <30.76%> (+11.09%)	0 <0> (ø)	⬇️
...nix/components/toolbar/BrowserToolbarController.kt	92.94% <80%> (-0.17%)	0 <0> (ø)
...lla/fenix/collections/CreateCollectionViewModel.kt	94.73% <94.44%> (+94.73%)	9 <8> (+9)	⬆️

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