python: add flux.job.JournalConsumer #3119

Job	Run time
python linting	26s
spelling	8s
validate commits	0s
Generate build matrix	10s
bookworm - test-install	30m 30s
bookworm - 32 bit	30m 30s
noble - test-install	30m 30s
el9 - test-install	30m 30s
alpine - test-install	30m 31s
fedora40 - test-install	1h 0m 30s
jammy - test-install	1h 0m 28s
focal - py3.8	17m 14s
bookworm - gcc-12,content-s3,distcheck	1h 0m 28s
fedora40 - clang-18	16m 52s
coverage	24m 46s
el8 - ascii	19m 41s
el8 - system,coverage	1h 0m 36s
inception	22m 38s
flux-pmix check	0s
flux-pam check	0s
flux-sched check	0s
flux-accounting check	0s
Generate docker manifest	0s
	8h 16m 28s

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