This change removes references to Observatory, including:
- Deprecated flags
- Deprecated embedder APIs
- Outdated documentation
- Documentation instances where "VM service" should have been used
- Incorrectly named tests / directories
As a part of this change, `--serve-observatory` is no longer a valid
flag.
Observatory is still available for now via the `_serveObservatory` RPC,
but will be removed in a follow up PR once we've prepared for breakages
in G3.
Work towards https://github.com/dart-lang/sdk/issues/50233
FYI @a-siva
Not so long ago I remember a very informal conversation that went something like this:
> @matanlurey: I wish I could pass `--dev` or something to `flutter` to run from source.
>
> @christopherfujino: I get what you want, but I don't want to overload the tool with more dev-only things. I would consider a script like `flutter-dev` that does that thing, though.
>
> @matanlurey: Cool, I might send a PR!
So uh, here it is 6-9 months later. Suggestions welcome.
