Add more services to `statemachine` example

[Yokozuna59]

Resolves #1257.

• validation

  • [x] Validate unreachable states
  • [x] Validate unused events

• code actions

  • [x] If a state name doesn't start with a capital letter, replace it with capitalized name (look at the corresponding validation here)
  • [x] Remove an unreachable state
  • [x] Remove an unused event

• LSP

  • [x] Formatter ~* [ ] RenameProvider~ (it's working fine)

I also validated commands with events and states.

I haven't implemented the full version of quick fix to make state name starts with capital letter yet. The current Langium LSP didn't implement such feature yet, so I'm not sure how to do it in a clean approach.

[Yokozuna59]

Sorry for the wait, but I have applied the comments in this PR.

Although I don't know how to make the ECA test pass, I have created an account there, but previous commits are failing.

[msujew]

@Yokozuna59 Can you squash your commits? I believe the ECA tool has some weird issue with some of your commits. Maybe you might also need to remove the verification requirement on your commits? All of them (except for the merge commit) say that they are Unverified.

[Yokozuna59]

@msujew I'm not really sure how to squash them when there's a merge-commit in between.

[Yokozuna59]

@msujew I squashed the commits and removed the commit verification, but the ECA is still failing.

[spoenemann]

@Yokozuna59 have you used exactly the same email address in your Eclipse account as in the Git commit?

[Yokozuna59]

@spoenemann Yes. Before rebasing and after creating the account, it showed that commits after that passed the test, but the original commits before creating the account still failed.