PHP: Revisit the default umask, consider 022

[adamziel]

Related to this Studio issue:

https://github.com/Automattic/studio/issues/269

tl;dr the permissions of files newly created by PHP.wasm are not aligned with the default unix values. It seems like an Emscripten-level issue:

https://github.com/emscripten-core/emscripten/issues/9916 https://github.com/emscripten-core/emscripten/issues/17269

We'll need either an Emscripten PR or a Playground-level patch.