serde: add `size` field to `Identifier` #4185

Job	Run time
Build cairo-vm-cli for base	2m 59s
Build cairo-vm-cli for head	3m 1s
Build Cairo programs for base	4s
Build Cairo programs for head	3s
Run benchmarks for modified programs	6s
Run benchmarks for unmodified programs	19m 17s
	25m 30s

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