Async Data Saving and Page Navigation - Introduce an asynchronous page navigation API which would lock UI while data is being saved to the server

[JaneSjs]

• T18556 - Survey Results (Partial) - Async Save / Saving State (Animation)
  https://surveyjs.answerdesk.io/internal/ticket/details/T18556
• T18537 - Async onCurrentPageChanging event
  https://surveyjs.answerdesk.io/internal/ticket/details/T18537

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Usage scenario:
Survey results are saved to a back-end server during survey completion. When users update question values, navigate between pages, or complete the survey, the survey data needs to be saved asynchronously to the server.

Desired Behavior:
Display a loading or saving indicator to inform users that their data is being saved.
Disable navigation buttons to prevent further actions until the saving process is complete.
If an error occurs, prevent the value change or page change and inform the user.

[mikeamelin]

Prototype to discuss — https://www.figma.com/design/jcuAUsN02n2yJerx39mqf9/LBR--%3E-Library-Preview?node-id=2485-15133