libflux: convert reactor to libuv #2497

Job	Run time
Generate build matrix	7s
validate commits	0s
python linting	29s
spelling	5s
bookworm - test-install	1m 11s
bookworm - 32 bit	1m 14s
noble - test-install	1m 19s
el9 - test-install	1m 22s
alpine - test-install	54s
fedora40 - test-install	1m 5s
jammy - test-install	1m 5s
focal - py3.8	1m 2s
bookworm - gcc-12,content-s3,distcheck	1m 7s
fedora40 - clang-18	1m 7s
coverage	1m 16s
el8 - ascii	1m 9s
el8 - test-install	1m 20s
el8 - system,coverage	1m 23s
inception	1m 12s
flux-pam check	1m 4s
macos build only	1m 27s
flux-accounting check	1m 6s
flux-pmix check	1m 5s
flux-sched check	1m 2s
Generate docker manifest	0s
	24m 11s

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