Increase minimum Node version to 18

[mikeharder]

The minimum Node version of all packages should be increased from 16 to 18, in part to allow us to use APIs only in Node 18 like fetch. (#1846).

typespec/packages/compiler/package.json

Line 47 in a5d648c

"node": ">=16.0.0"

[timotheeguerin]

Node 16 has now reached EOL as of today. https://nodejs.org/en/blog/announcements/nodejs16-eol

So we should schedule this, there is nothing urgent right now but dependencies might start to stop working on node 16 and/or setup their own engine requirement.

[markcowl]

est: 3

[markcowl]

Describe the breaking change
Node version 16 is out of support, remove nofe16 from node engine versions in package.json, consumers should end usage of node 16 (otherwise, warning)

Back-compat design to avoid immediate breaking
Any back-compat design: Verified with DPG team no node16 usage in pipelines

Link to detailed breaking design

Impact
This change affecting:

• ARM
• Data-plane
• Existing specs: approx. # of service/spec impacted
• New specs
• Emitters
• SDK

Targeted Sprint
Sprint: November

Additional information