cache R in the job manager #7725

Job	Run time
python linting	47s
validate commits	16s
spelling	7s
Generate build matrix	10s
bookworm	29m 17s
bookworm - 32 bit	24m 29s
bookworm - gcc-12,content-s3,distcheck	26m 26s
bookworm - py3.11,clang-15	23m 59s
coverage	36m 20s
jammy - test-install	16m 45s
bookworm - test-install	19m 32s
focal - py3.8	28m 3s
el8	35m 18s
el8 - ascii	35m 46s
el8 - system,coverage	8m 57s
fedora34 - gcc-11.2,py3.9	23m 49s
fedora38 - gcc-13.1,py3.11	22m 23s
inception	23m 45s
flux-sched check	10m 46s
flux-pmix check	19m 38s
flux-accounting check	6m 17s
flux-pam check	5m 59s
Generate docker manifest	1s
	6h 38m 50s

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