[dynamo] Make tx.next_instruction lazy (#122066)
Improves benchmarks/dynamo/microbenchmarks/dynamo_microbenchmarks.py
from 2.5s to 2.4s.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/122066
Approved by: https://github.com/oulgen, https://github.com/anijain2305
ghstack dependencies: #122039, #122043, #122055, #122058, #122060, #122063
