feat!: use Web API's fetch

[slagiewka]

Currently not working due to no possible way to set the url prop of Response in cases where the lib tries to fake it once retrieved from cache.

Included:

• drop node-fetch@v2
• update nock to v14
• raise minimal node version to 20 (as 18 is almost EoL)
• raise ES target to match node 20

Closes #393