test_runner: add mock-timers support for AbortSignal.timeout #959

Job	Run time
Build slim tarball	1m 26s
x86_64-linux: with shared libraries	29m 7s
x86_64-darwin: with shared libraries	40m 0s
aarch64-darwin: with shared libraries	21m 49s
aarch64-linux: with shared libraries	24m 53s
	1h 57m 15s

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