test: split test-runner-run-watch.mjs #816

Job	Run time
Build slim tarball	1m 35s
x86_64-linux: with shared libraries	27m 58s
aarch64-linux: with shared libraries	24m 22s
x86_64-darwin: with shared libraries	35m 47s
aarch64-darwin: with shared libraries	23m 4s
	1h 52m 46s

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