fix(test): handle snippet containing Deno.test in doc test

[scarf005]

fixes #29629

skips wrapping code snippet in Deno.test if it already has one.

# Title

```ts
import { assertEquals } from "@std/assert/equals";

Deno.test("add", () => {
  assertEquals(1 + 2, 3);
});
```

this feature is useful when doctest itself uses Deno.test inside the snippet, such as https://docs.deno.com/examples/mocking_tutorial/.

known issues: will false-positive on Deno.test inside multiline comments but such cases should be rare

[kt3k]

This option sounds confusing to me. How about detecting the usage of Deno.test automatically and avoid wrapping when Deno.test is used (I think it's ok for the detection to have false positives and false negatives if it supports main use cases)

[scarf005]

@kt3k could i get pointers on how to detect Deno.test?

[kt3k]

Deno.test should be used at top-level or at least top-level of blocks in most practical cases. I think it's practically fine to detect it by the regexp of /^\s*Deno.\.test\(/ for each line.

[scarf005]

@kt3k applied and force-pushed in be81dba (#29631)

[kt3k]

LGTM

I also like to hear opinions from @bartlomieju @dsherret @nathanwhit

[bartlomieju]

Seems quite niche, but I'm fine with this solution, +1 from me

[dsherret]

LGTM too