Update supported versions of node

[aabmass]

The packages in this repository support all officially supported Node.js versions.

Current supported node versions are 18, 20, (and soon 21).

• Update CI to support only newest versions
• Upgrade dependencies which don't support older versions
  • Remove overrides for nx or merge chore(deps): update nx to v16.10.0 #633
  • chore(deps): update all non-major dependencies #646
• Upgrade @types/node chore(deps): update dependency @types/node to v18 #441
• Make a major version bump release. Include other upcoming breaking changes at the same time, e.g.
  • Upgrade to Typescript 5 chore(deps): update dependency typescript to v5.2.2 - autoclosed #607
  • Get rid of deprecated async GcpDetector

I'd like to make one more minor version release before doing this.

[aabmass]

I am planning to address this when the GCP client libraries also drop support for older node versions.