solver: add more debug logs to track down inconsistent graph state #7313

Job	Run time
archutil-arm64	0s
prepare	6s
validate (lint-default)	12m 19s
validate (lint-labs)	12m 29s
validate (lint-nydus)	12m 18s
validate (lint-proto)	24s
validate (lint-yaml)	22s
validate (validate-archutil)	37s
validate (validate-docs)	54s
validate (validate-doctoc)	28s
validate (validate-generated-files)	43s
validate (validate-shfmt)	22s
validate (validate-vendor)	27s
	41m 29s

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