Update faker-js/faker to v6

[BPScott]

Description

Update faker-js/faker to v6 so we don't need to do weird hacks to provide types for the package.

I've updated calls to deprecated behaviour. Searching the CI test logs for 'faker' should result in no deprecation warnings logged to the console.

Type of change

• graphql-fixtures: major

Noticed issue

[ryanwilsonperkin]

Looks like the latest version is incompatible with Node <14
We support v12 at the moment but it leaves LTS in ~a month, we could wait to ship this or preemptively drop support for 12. Any standard practice that we follow in this case?

[BPScott]

I'd prefer to explicitly drop support for node 12 by updating engines fields and updating the version we target when building, and then merge this PR.

Considering Shopify internally doesn't support node 14 anymore thanks to everyone using M1s there's an argument to be made for dropping support for v14 too, but that's pretty agressive

[ryanwilsonperkin]

+1 to dropping node 12, agreed that we should keep node 14 since its LTS

[BPScott]

Rebased atop of #2277, which drops support for node 12.