Consider importing Analyzer-server docs to the new Analysis-server-plugin docs

[rrousselGit]

Hello!

Currently analysis_server_plugin docs are a little bit limited. They are a good start, but lots of things are left unsaid.
Looking for more (such as what MultiCorrectionProducer is for), I spotted https://github.com/dart-lang/sdk/blob/bc165fd5e148d89ee053b9b9c5ad29b9fae96b0e/pkg/analysis_server/doc/implementation/quick_fix.md

I feel like those couple of docs are quite valuable. I assume it would be beneficial to reuse them for the plugin system

Maybe instead of the current docs, we could use those docs. And the parts about "bulk fixes" would be flagged as "Currently unsupported by external rules/fixes" until it is officially supported too.

[FMorschel]

CC @srawlins @bwilkerson

[srawlins]

Good call.