drop any fetch dependencies

[tsamaya]

As now node since version 18 has a fetch() function built-in and all browsers have this function, I think it is time to get rid of dependencies. That would lighten the package and also narrow down security risks raised by Meterian's report with the old version of node-fetch used by cross-fetch

[tsamaya]

It makes sense to drop cross-fetch dependency in version 2, dropping the support for node < 18 as well.