Drop Node.js 16, upgrade minimal 18 and 20, test 21 #1418

Job	Run time
Test package-lock for unexpected modifications	24s
TypeScript compatibility (~5.1)	19s
Node.js (^18.18, ubuntu-latest)	3m 28s
Install dependencies without using a lockfile	6m 9s
Node.js (^18.18, windows-latest)	9m 47s
Lint source files	39s
Node.js (^18.18, macos-latest)	5m 56s
Node.js (^20.8, ubuntu-latest)	5m 51s
Node.js (^20.8, windows-latest)	8m 9s
Node.js (^20.8, macos-latest)	6m 19s
Node.js (^21, ubuntu-latest)	7m 4s
Node.js (^21, windows-latest)	7m 29s
Node.js (^21, macos-latest)	5m 1s
	1h 6m 35s

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