version_42: Global optimization fixes (#1360)

* run dfe at the very end, as it may be more effective after inlining

* optimize reorder-functions

* do a final dfe in asm2wasm after all other opts

* make inlining deterministic: std::atomic<T> values are not zero-initialized

* do global post opts at the end of asm2wasm, and don't also do them in the module builder

* fix function type removing

* don't inline+optimize when preserving debug info