test: improve test-fs-access error validation

[edsadr]

use better RegExp to validate the errors in assert.throws

Checklist

• make -j4 test (UNIX), or vcbuild test (Windows) passes
• tests and/or benchmarks are included
• commit message follows commit guidelines

Affected core subsystem(s)

test

[Trott]

LGTM if CI is green.

[Trott]

Nit: err is unused. Remove it?

[Trott]

Nit: While we're in here refactoring, maybe change the rocket function on lines 117-119 from this:

(err) => {
   return err.code === 'ENOENT' && err.path === doesNotExist;
 }

...to this?:

(err) => (err.code === 'ENOENT' && err.path === doesNotExist)

Both styles show up in our code base, but the latter (no unnecessary braces + return) is far more common and I'd like to see things inch towards a common style that can then be enforced by a lint rule.

[edsadr]

@Trott , did the Nits... sorry it took a little bit... had a hard week

[italoacasas]

CI: https://ci.nodejs.org/job/node-test-pull-request/

[edsadr]

Closing this one in favor of #11087