Feature request: flavor = "multi_thread" support for #[sqlx::test]

[vikanezrimaya]

Is your feature request related to a problem? Please describe.
From documentation:

#[sqlx::test] does not recognize any of the control arguments supported by #[tokio::test] as that would have complicated the implementation. If your use case requires any of those, feel free to open an issue.

Thus this issue.

Describe the solution you'd like

#[sqlx::test(tokio_flavor = "multi_thread", tokio_threads = 1)]

Describe alternatives you've considered

• Reimplementing #[sqlx::test] manually in my project without a macro
  • Tedious
• A second macro that would spawn a multi-threaded runtime
• Having #[sqlx::test] not spawn a runtime for non-async functions May not be feasible due to how the macro is structured
  • This would allow me to bring my own #[tokio::test] invocation, since the Tokio macros de-asyncifiy the functions they're used on.
• Just spawn a multi-threaded runtime by default

Additional context
n/a

[abonander]

I'd accept a PR to support this:

#[sqlx::test(tokio(...))]

and then we don't have to parse ..., we can just pass it directly to #[tokio::test(...)].

The problem is, that's not currently how it works internally (it expands to more than just #[tokio::test]), so we'd need to move some stuff around.