Allow extensions to extend vue instance configuration

[cnotv]

Description

Allow extensions to add elements like custom components, libraries, or error handlers for error tracking.

E.g.: https://github.com/cnotv/sentry-rancher-extension

Context

In the current implementation, extensions logic includes the Vue instance attribute but is not passed as an argument. It is impossible to inherit it within the extensions and add further capabilities.

[cnotv]

Closing issue due discussion in PR #12629