Allow using complex types in try_from when deriving FromRow

[95ulisse]

Hello 👋

The new attribute try_from for the FromRow derive introduced by #1081 expects the value of try_from to be a simple identifier instead of a full-fledged type. This means that that attribute cannot be used unless the referenced type is already in scope.

#[derive(sqlx::FromRow)]
struct Record {
    #[sqlx(try_from = "SomeType")] // <- This is fine
    id: u64,
}

#[derive(sqlx::FromRow)]
struct Record {
    #[sqlx(try_from = "another::SomeType")] // <- This currently fails, but it should be allowed
    id: u64,
}

This PR allows using complex types as the argument of try_from instead of just simple identifiers.

[abonander]

@95ulisse current development is on the 0.7-dev branch which just had some major refactors merged. Do you mind rebasing?

[95ulisse]

@abonander I've just rebased my PR on top of 0.7-dev 👍

[abonander]

@95ulisse can you amend and force-push to trigger a Github Actions run?

[95ulisse]

@abonander Done 👍 The workflow is now pending approval.

[95ulisse]

@abonander I fixed the tests and they are green on my machine. Could you re-run the workflow when you have some time, please? 🙏