Code Quality: Use thread-safe collections in ItemViewModel

[hishitetsu]

I believe this may avoid crashes like #12924.

Resolved / Related Issues

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  Related to Code Quality: Use thread-safe collections if accessed by multiple threads #12617

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[ferrariofilippo]

I think you forgot to do something in the Remove* methods

[hishitetsu]

@ferrariofilippo thank you for reviewing. I'll check when I have more time.
Incidentally, this was created by referring to BulkConcurrentObservableCollection and removing unnecessary code.
https://github.com/files-community/Files/blob/794e7e489aa34690457bdd661972486274e284c8/src/Files.App/Helpers/StorageItemCollection/BulkConcurrentObservableCollection.cs

[hishitetsu]

I think you forgot to do something in the Remove* methods

Fixed except for one point.

[ferrariofilippo]

LGTM