Better way to resolve binary path when `node_modules/` doesn't exist

The issue is similar to https://github.com/rescript-lang/rescript-vscode/issues/638.

Affected setup

• Native Deno project, where packages are only installed into Deno's global cache and no node_modules/ compatibility directory is exposed.
• Yarn-berry project in PnP mode (pnpm also supports this setup) where all dependencies are installed into Yarn's global cache as ZIP archives and they are resolved using a JS loader file at project root.
• The user might want to use rescript/rewatch binary packaged by a downstream distribution (.e.g Nixpkgs)

Setting a custom value for settings.platformPath / settings.binaryPath is undesirable since the parent directory of the binary might not be obvious (in case 2 and 3 above).

Suggestion

We could have special logic to deal with Deno and PnP cases, and optionally search the user's PATH for the binary if they want to.

Start by tracing how settings.platformPath and settings.binaryPath currently resolve the rescript/rewatch binary, then compare that flow with the native Deno and Yarn PnP setups described here. Done means a decided resolution strategy for those cases, including optional PATH lookup, with behavior verified for the affected setups.