fix: use hygenic macro path

[alexander-jackson]

When the #[sqlx::test] macro is imported using #[macro_use] such as in the following example:

extern crate sqlx;

mod tests {
    #[test]
    fn something() {}
}

then the #[test] generated by the macro will refer to itself instead of the standard Rust #[test] macro. This will cause rustc to recursively expand it and produce the following error message:

thread 'rustc' has overflowed its stack
fatal runtime error: stack overflow

Instead, we can just refer to the standard macro by using its fully qualified path.

This PR:

• Swaps #[test] usages in #[sqlx::test] for their hygenic path to prevent recursive expansion alongside #[macro_use]

Closes #2017.