solver: move scheduler debug statements to their own functions #4799

Job	Run time
govulncheck	54s
prepare	5s
binaries (darwin/amd64)	1m 14s
binaries (darwin/arm64)	1m 0s
binaries (linux/amd64)	1m 59s
binaries (linux/arm/v7)	1m 52s
binaries (linux/arm64)	2m 6s
binaries (linux/s390x)	1m 58s
binaries (linux/ppc64le)	1m 55s
binaries (linux/riscv64)	2m 11s
binaries (windows/amd64)	1m 40s
binaries (windows/arm64)	1m 37s
test / prepare	1m 47s
test / run (containerd, ./client ./cmd/buildctl ./worker/containerd ./solver ./frontend, integration)	7m 49s
test / run (containerd-rootless, ./client ./cmd/buildctl ./worker/containerd ./solver ./frontend, integr...	9m 3s
test / run (containerd-1.6, ./client ./cmd/buildctl ./worker/containerd ./solver ./frontend, integration)	33m 8s
test / run (containerd-snapshotter-stargz, ./client ./cmd/buildctl ./worker/containerd ./solver ./fronte...	9m 21s
test / run (oci, ./client ./cmd/buildctl ./worker/containerd ./solver ./frontend, integration)	5m 52s
test / run (oci-rootless, ./client ./cmd/buildctl ./worker/containerd ./solver ./frontend, integration)	6m 0s
test / run (oci-rootless-slirp4netns-detachnetns, ./client ./cmd/buildctl ./worker/containerd ./solver ....	6m 46s
test / run (oci-snapshotter-stargz, ./client ./cmd/buildctl ./worker/containerd ./solver ./frontend, int...	5m 12s
test / run (./..., 1, integration gateway)	5m 53s
test / run (./client, containerd, nydus, integration)	7m 53s
test / run (./client, oci, nydus, integration)	6m 0s
test / run (./..., nydus, 1, integration)	5m 2s
image	0s
release	0s
scout	0s
	2h 8m 17s

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