Tracking issue: implementation of RFC005

[yannham]

Tracking issue for the implementation of RFC005 (#819).

• Restrict metadata to record fields only ([RFC005 Implementation] Restrict metadata to record field #953, [RFC005] First phase of RFC005: field metadata #990)
• Lazy propagation for contracts ([RFC005] Lazy propagation #1086)
• Reduce the performance overhead of lazy propagation, e.g. by caching contract application over record fields ([RFC005] Lazy propagation #1086 (comment))
• Improve the handling of dynamic fields, and how their metadata and pending contracts are transferred ([RFC005] Lazy propagation #1086 (comment))