kvs: add transaction stats #10111

Job	Run time
python linting	32s
Generate build matrix	10s
validate commits	13s
spelling	6s
bookworm - test-install	12m 24s
bookworm - 32 bit	13m 14s
noble - test-install	13m 2s
el9 - test-install	12m 30s
alpine - test-install	13m 33s
fedora40 - test-install	12m 14s
jammy - test-install	11m 51s
focal - py3.8	16m 51s
bookworm - gcc-12,content-s3,distcheck	19m 3s
fedora40 - clang-18	17m 0s
coverage	23m 46s
el8 - ascii	19m 27s
el8 - test-install	13m 44s
el8 - system,coverage	7m 3s
inception	20m 49s
flux-sched check	6m 59s
flux-pam check	4m 8s
flux-accounting check	4m 51s
flux-pmix check	12m 52s
macos build only	3m 36s
Generate docker manifest	0s
	4h 19m 58s

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