[EPIC][UI - Wallet Stability] Wallet root store and shared store improvements

[noeliaSD]

Description

There are some stores that are declared as Singletons. This fact introduce the following issues, among others:

• It creates a dependency on context properties.
• It breaks unit tests / storybook pages.
• It makes the code more complex and has dificult maintenance.
• Some components become copled and not isolated.

By following the approach agreed in here, work on updating these stores:

1. status-desktop/ui/app/AppLayouts/Wallet/stores/RootStore.qml
2. status-desktop/ui/imports/shared/stores/RootStore.qml

Tasks:

• Make stores typed and disambiguated by prefixes if needed #14801
• Wallet's RootStore: make all properties read-only #14802
• Wallet's RootStore: hide private properties in d object #14803
• Wallet's RootStore: Exclude backend-independent methods to stateless singleton utility component #14804
• Remove custom rowData method from nim's models #14805
• TODO (the list is not complete)

[noeliaSD]

@micieslak please take a look at it and break it down if necessary!