fix: Always call coverage initialization function

[coreyfarrell]

Ensure that sources initialize coverage data even if no code is run.

---

The primary use case for this is ES modules that are not transpiled to CJS. For example create fn1.js:

export function fn1() {
  console.log('test');
}

And index.js:

import {fn1} from './fn1.js';

if (false) {
  fn1();
}

The expected result is for fn1.js to be reported as zero coverage but since the file has code but does not execute any top-level code it never gets in this test case.