stdin read seems racy

This line when reading stdin seems racy:

https://github.com/denoland/node_deno_shims/blob/bd4a83ef3fb0788541191e4a089563c63da6cd1f/packages/shim-deno/src/deno/stable/variables/std.ts#L29

I think it's possible that between the `process.stdin.read(p.length)` and `process.stdin.read()` calls that stdin could receive more bytes than are in the buffer, which would cause a `RangeError`.