Reduce Add/RemoveIndex migration operations. Description

Reduce Add/RemoveIndex migration operations. Description: a task in Lego-RL-SWE-Bench-Verified (Harbor dataset). We should reduce AddIndex/RemoveIndex operations when optimizing migration operations.

The task

We should reduce AddIndex/RemoveIndex operations when optimizing migration operations.

Part of Lego-X/Lego-RL-SWE-Bench-Verified.