feat(react-cap-theme): add CAP component wrappers and separate from published customStyleHooks

[GianoglioEnrico]

Overview

This PR proposes a restructuring of the react-cap-theme package to clearly separate the published style hooks (src/customStyleHooks/) from internal-only component wrappers (src/components/).

Some Fluent UI components require API changes (e.g. new appearances, additional props) that cannot be achieved through customStyleHooks_unstable alone. These components need full wrappers that compose custom state, styles, and rendering.

The package continues to export only the custom style hooks as its public API, but defining full component wrappers allows us to test the final CAP components end-to-end.

Component architecture

The internal components are built by calling the base Fluent style hooks first and then applying the CAP overrides on top, making them self-contained — they don't depend on customStyleHooks_unstable being injected via FluentProvider. This means they can also be reused in applications where, for technical reasons, it is not possible to use the FluentProvider injection mechanism.

cc: @dvdzkwsk