port test_function to CTS

[bavulapati]

ports
test_function from the Node.js test suite to the CTS.

[bavulapati]

@legendecas Fixed the lint issue. Can we run the tests again?

[kraenhansen]

Verification: Test code compared against upstream Node.js

I compared the test files in this PR against the upstream Node.js source at test/js-native-api/test_function/.

C File: Identical

• test_function.c — byte-for-byte identical to upstream

JS File: Mostly Expected Harness Adaptations

test.js has the standard mechanical changes, plus one behavioural difference:

1. Quote style — single quotes → double quotes (prettier)
2. Imports replaced with CTS globals — require('assert'), require('../../common'), etc. replaced with loadAddon(), and CTS globals (assert, mustCall)
3. global.gc() → gc() — uses CTS global directly
4. Prettier formatting — trailing commas, multi-line reformatting

One non-mechanical change

• func2: console.log('hello world!') removed — the upstream function body contains a console.log call before return null;, which was removed in this port. This is a minor behavioural difference: the upstream test exercises calling a JS function that has a side-effect (console output) before returning, whereas the ported version only returns null. Unlikely to affect test correctness, but worth noting as a deviation from verbatim.