After then, we can merge the logic of expr_simplifier and dead_branch_remover into the pure optimizer.

• Pure optimizer: https://github.com/swc-project/swc/tree/8f8dcaac2f22f71de538802034db5756e84c7f55/crates/swc_ecma_minifier/src/compress/pure

• Target directory: https://github.com/swc-project/swc/tree/8f8dcaac2f22f71de538802034db5756e84c7f55/crates/swc_ecma_transforms_optimization/src/simplify

Points

• This task is required because of the versioning issue. transform() API of SWC supports simplify, so we can't simply move the logic of expr_simplifier and dead_branch_remover to the pure optimizer.

Instead, we need to move the pure optimizer to the simplifier first, and use it for the simplify option. After then, merging logic will be safe.

• The configuration for pure optimizer should use #![non_exhaustive], so adding a field is not a breaking change.

• The expected gain is 5% ~ 10% of total runtime. It's mainly due to less visit, and also due to parallelization being more efficient.