Stabilize Filesystem regions and mount output

[Icemap]

Summary

• replace runtime Drive9 manifest lookup with four built-in TiDB Cloud Filesystem region mappings and normalize Alibaba Cloud placement to alicloud-ap-southeast-1 while accepting legacy local credentials
• suppress misleading Drive9 startup and unmount guidance after successful background mounts while retaining foreground output and failure diagnostics
• simplify installer output, publish the static Filesystem region list, and fix seven user-visible help-text typos

Validation

• make test
• make e2e
• make live-e2e-fs
• git diff --check