Support for wasi_snapshot_preview1

[fgsch]

While it's possible to change the module via go:wasm-module and use wasi_snapshot_preview1, I've encountered an issue (I will open a separate ticket) that makes this not ideal for my use case.

I was wondering if TinyGo could switch WASI to use wasi_snapshot_preview1, the latest version, instead of wasi_unstable by default?

[aykevl]

Please take a look here: #1690

[fgsch]

Oh, I didn't see this and I worked on the change myself. Sorry!
There are a few more things my PR covers so I will open it and you can decide.

[deadprogram]

This was released with v0.18 so now closing. Thank you!