rfc: add a reduced rollup for the core of `fast-element` and change the current bundle to `fast-element.all`

[chrisdholt]

💬 RFC

The current rollup bundle for fast-element includes everything that is currently available with FAST. With that, the size of importing fast-element itself as a module for basic needs is significant.

The goal of this is to provide the best of both worlds - a lean rollup of only what is necessary to render a custom element, and a larger "all" rollup which would include additional considerations such as directives, etc.

This may technically be a breaking change for those who use the CDN or who import fast-element.js as ESM from the package dist, so we'd like feedback from the community to gauge interest in this change and slight performance optimization for basic use cases.