apollo-plugin: Update engines stanza to `>=18` in package.json and all test/versioned package.json and remove 16 from CI

[bizob2828]

Description

To officially drop support for node 16 we need to update the engines stanzas in package.json in root and test/versioned.

[workato-integration]

https://new-relic.atlassian.net/browse/NR-286213