Use `package:package_config` to pass `--packages` to all `dart compile` subcommands

[bkonyi]

Each of the various tools invoked by dart compile are currently responsible for discovering the correct package-config.json if one isn't explicitly provided. We should instead move discovery into the dart compile subcommands in the CLI and always pass --packages to the tooling.

[bkonyi]

@sigurdm, I was going through my issue backlog and came across this. Is this something that's worth doing? If so, what's the best way to go about doing it using package:package_config?

[lrhn]

Seems like #55548 is related to this issue.
It doesn't use package:package_config directly because it has to look for pubspec.yaml too.

[sigurdm]

I think dart compile <foo> should invoke the getExecutableForCommand like dart run currently does. That would let pub find the relevant package config, and also allow things like:

dart compile <package>:<executable>

to reference bin/<executable>.dart inside a dependency's package dir. And it would make sure that dependencies are resolved and up-to-date before compiling.