Single entry slot map

[aardvark179]

Single entry slot map

This is a stacked PR on top of

• Reduce indirection and memory overhead for slot maps. #1782
• Start to factor out slot map container #1783

This introduces a single-entry slot map to take the common case of a single property from:

graph LR
Object["ScriptableObject"]
Map["SlotMap"]
Array["Slot[]"]
Slot1["Slot"]
Object1["ScriptableObject"]
Map1["SlotMap"]
Array1["Slot[]"]
Slot2["Slot"]
Object --> Map --> Array
Array --> Slot1
Object1 --> Map1 --> Array1
Array1 --> Slot2

Loading

to:

graph LR
Object["ScriptableObject"]
Map["SingleEntrySlotMap"]
Slot1["Slot"]
Object1["ScriptableObject"]
Map1["SingleEntrySlotMap"]
Slot2["Slot"]
Object --> Map --> Slot1
Object1 --> Map1 --> Slot2

Loading

This saves 48 bytes on any object with a single slot.

[aardvark179]

Rebased after merge of #1782.