[codex] Improve mdm table tests

[grahamgilbert]

Summary

• make MDM profile/status helpers injectable for deterministic tests
• add enrolled and unenrolled generator coverage
• cover profile command/plist errors and enrollment status parsing errors
• use the passed filesystem when checking for the profiles binary

Validation

• GOCACHE=/tmp/osquery-extension-go-cache go test ./tables/mdm
• GOCACHE=/tmp/osquery-extension-go-cache go test ./...