chore: introducing fast-check feature

[AlseinX]

The current build scripts of the wasm(runtime) projects runs wasm builds unconditionally, which makes cargo check(which is called by rust-analyzer on save to perform compilation checks) extremely slow.
I added a feature switch to disable these scripts when cargo check is called by rust-analyzer.

This feature is never used on build, just for rust-analyzer only, with the following config:
.vscode/settings.json :

{
    "rust-analyzer.check.features": [
        "fast-check"
    ]
}