AC: Vite as a primary frontend build tool

[mshabarov]

Description

Make Vite as a primary tool for building Vaadin frontend, make Webpack as an optional tool available behind the feature flag, see vaadin/flow#13852.

Use cases

As a developer
I want to have a faster build, startup and hot reloads of my Vaadin applications
So to have a better developer experience and faster development process.

Acceptance criteria

• The offline path is requested regardless of the original path when online in dev mode issue is fixed
  - [ ] Vite projects do not work with pnpm 7 is fixed
• Vite is used by default, Webpack is behind a feature flag
• Documentation updated accordingly.
• Vite tests covers at least the same amount use cases as for Webpack.

General criteria

• Performance

• UX/DX tests in Alpha

• Documentation:

• How to test?

• Limitations: