Fix LGSM install reruns

[MarcStdt]

Summary

• make LGSM install refresh safe to rerun against persistent server directories
• replace stale linuxgsm.sh and lgsm/modules before moving fresh LinuxGSM files
• regenerate LGSM scroll outputs from the existing build source

Test Plan

• env GOCACHE=/private/tmp/druid-go-cache make build-tree
• env GOCACHE=/private/tmp/druid-go-cache go test ./scripts/prebuild ./scripts/validate-release-workflow
• env GOCACHE=/private/tmp/druid-go-cache go run ./scripts/validate-scrolls.go
• env GOCACHE=/private/tmp/druid-go-cache ./scripts/validate_all_scrolls.sh

[druid-infra]

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