[Bug] Implementors of `IPartialShareProvider`s use str_replace to replace `/{user}/files`

[salmart-dev]

Description

Share providers implementing IPartialShareProvider are currently removing /{user}/files from the provided path using str_replace which replaces the string from any position in the path. The wanted behaviour is to do this only at the beginning of the path.

Providers to fix:

• DefaultShareProvider -> fix: remove user part only at the beginning of path #58338
• ShareByCircleProvider -> fix: remove user part only at the beginning of path circles#2367
• DeckShareProvider -> fix: remove user part only at the beginning of path deck#7642
• RoomShareProvider -> done in [stable33] perf(sharing): Split getShareWith() and shortcut the happy path with $path spreed#17097