feat: add support for the skip_teardown keyword

[JasterV]

Introducing a new flag to skip the context teardown

Sometimes on the setup we are not performing an operation that requires a teardown operation such as closing a connection with a remote server.

For this scenario I am introducing a new keyword skip_teardown that can be used on the test_context macro to skip the teardown and take full ownership of the context.

An example:

struct Context {}

impl AsyncTestContext for Context {
    async fn setup() -> Self {
        Self {}
    }

    async fn teardown(self) {
        panic!("boom!");
    }
}

#[test_context(TeardownPanicContext, skip_teardown)]
#[tokio::test]
async fn test_async_skip_teardown(mut _ctx: Context) {}

In the example above the test won't panic because we are skipping the teardown.
Also, because now we don't need to pass the value to the teardown function we can safely pass full ownership of the context to the test.