refactor: update fetch import for node v21+ compatibility

[avallete]

Description

• Use global fetch first, fallback to cross-fetch if needed
• Addresses deprecation warnings due to unresolved issues in cross-fetch, node-fetch, and whatwg-url libraries
• Ensures compatibility with environments running node.js v21+ where punycode module is deprecated

Related Issue

I've been following those issues on node-fetch https://github.com/node-fetch/node-fetch/pull/1793 And on cross-fetch https://github.com/lquixada/cross-fetch/issues/177

Both seems stale, so I hope that we can fix quicktype-core in the meantime. I've used the solution recommended into the cross-fetch issue toward conditional import and using native node fetch if available.

Motivation and Context

We're using quicktype-core in some of our tools, one of them being a cli tool, every-time a command is ran the deprecation coming from quicktype-code cross-fetch dependency shows up on node >=v21.

Previous Behaviour / Output

(node:6629) [DEP0040] DeprecationWarning: The `punycode` module is deprecated. Please use a userland alternative instead.
(Use `node --trace-deprecation ...` to show where the warning was created)

New Behaviour / Output

No warning output.

How Has This Been Tested?

1. Build and pack the quicktype-core package locally with the change
2. Change my project quicktype-core dependency to point to the local builded package tgz and install
3. Used FetchingJSONSchemaStore in node scripts to trigger the fetch behaviour with node versions 16.20.1, 18.20.2 and 21.7.3
4. Build my project cli tool, and run it over with node versions v16.20.2, v18.20.2, v21.7.3 expected behaviour occurs and the warning is gone.

Screenshots (if appropriate):

[dvdsgl]

Thank you! Warnings be gone!