Share analysis results with a running analysis server

[tylandercasper]

Since 99% of build_runner time is anaylzing files, and we've already done that if we're running vscode or Android Studio, is it possible for build_runner to just use the existing LSP server to do it's parsing?

In theory this allow us to make changes with the same speed of build_runner watch

[davidmorgan]

Actually--based on the benchmarking I've been doing--very little of build_runner's time on big projects is spent analyzing files.

So the first optimization is to speed things up so analyzing files really is most of the work.

After that, yes, it might make sense to share work with another running analyzer instance.