Refactor prompt and settings view providers to use namespaced handlers and extract shared prompt utility functions

- [Pasted text] `apps/editor/src/views/prompt/backend/utils`
- create barrel file in utils in `apps/editor/src/views/prompt/backend/utils`
- for [Fragment] use {* as handlers)
- for [Fragment] use {* as state_keys)

└── apps
    └── editor
        └── src
            ├── commands
            │   └── check-for-updates-command.ts
            ├── utils
            │   └── check-for-updates.ts
            └── views
                ├── prompt
                │   └── backend
                │       ├── prompt-view-provider.ts
                │       └── utils
                │           ├── estimate-token-count.ts
                │           ├── get-display-path-for-editor.ts
                │           ├── get-valid-web-configurations.ts
                │           ├── index.ts
                │           ├── insert-text-at-caret.ts
                │           ├── persistent-text-storage.ts
                │           ├── preview-text-in-temp-file.ts
                │           ├── symbols
                │           │   ├── fragment
                │           │   │   └── replace-fragment-symbol.ts
                │           │   ├── git
                │           │   │   └── replace-git-symbols.ts
                │           │   ├── image
                │           │   │   └── replace-image-symbol.ts
                │           │   ├── pasted-text
                │           │   │   └── replace-pasted-text-symbol.ts
                │           │   ├── replace-symbols.ts
                │           │   ├── saved-context
                │           │   │   └── replace-saved-context-symbol.ts
                │           │   ├── skill
                │           │   │   └── replace-skill-symbol.ts
                │           │   ├── snippet
                │           │   │   └── replace-snippet-symbol.ts
                │           │   ├── symbol-cache.ts
                │           │   └── website
                │           │       └── replace-website-symbol.ts
                │           └── website-fetcher.ts
                └── settings
                    └── backend
                        └── settings-view-provider.ts

Author: robertpiosik