Coarse-graining support: Support.CoarseGraining.MuRecovery

Imported from the Apache-2.0 CoarseGraining development at commit c7ddd76c08ade64fed1b8d2ca51be14dfee8deb4.

Mu recovery (aggregate re-export)

Previously a 2111-line monolithic module whose MuCorrectionSpaceRecoveryData namespace alone spanned ~1560 lines; now split along namespace / theme boundaries into the five files imported above. Shim for backward compatibility.