Drop node 12

[mroderick]

This PR drops support for Node 12 and adds support for Node 18.

Purpose (TL;DR) - mandatory

How to verify

1. Check out this branch2.
2. nvm install 18
3. npm install
4. npm test
5. Observe tests pass
6. ... or observe that the tests pass in Node 18 in GitHub Actions :)

Checklist for author

• [x] npm run lint passes
• [x] References to standard library functions are cached.

[codecov[bot]]

Codecov Report

Merging #2454 (7034d47) into main (18d5601) will not change coverage. The diff coverage is n/a.

:exclamation: Current head 7034d47 differs from pull request most recent head 0e97c26. Consider uploading reports for the commit 0e97c26 to get more accurate results

@@           Coverage Diff           @@
##             main    #2454   +/-   ##
=======================================
  Coverage   95.97%   95.97%           
=======================================
  Files          39       39           
  Lines        1888     1888           
=======================================
  Hits         1812     1812           
  Misses         76       76           

Flag	Coverage Δ
unit	95.97% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
lib/sinon/default-behaviors.js	100.00% <ø> (ø)

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[mroderick]

This has been published to the npm registry as sinon@14.0.0