add aggressive-memory-offset-merging pass to merge offset and previous const

[HerrCai0907]

This pass is more aggressive optimization which assumes memory visit instruction will not overflow during arithmetic operations. Out of bound memory usages are either UB (e.g. C++) or protected / checked in high level language design (Assemblyscript, Go, etc...). Introducing this pass can reduce the work load of WASM runtime and may helpful to code size in some corner cases.