Rollback snapshot restore performance optimisations

[albertok]

Found some simple but meaningful performance wins in the hotpath that is recording and restoring in rollback.

Mostly by avoiding copying and type checking functions.

Found a way to offload the dict iteration to Godots internal functions.

Consolidated a duplicate property read.

Perf comparison of 16 Nodes with 4 properties.

Test    Before (it/s)    After (it/s)    Gain
record()    5,388        6,829          +26.7%
restore()   11,961       14,573         +21.8%