Improvements on Exposed ORT support

[kallebysantos]

Hey there 🙏,
Coming from #947, I did test the new Exposed ORT feature in alpha-v20 and alpha-21 releases. I'd notice that to make it work we must specify 'auto' as inference device:

Current behaviour:

Without specify a device:

import { pipeline } from '@huggingface/transformers';

let pipe = await pipeline('sentiment-analysis');
// The exposed runtime is loaded 
// but when trying to inference:
let out = await pipe('I love transformers!');
//Error: Unsupported device: "wasm". Should be one of: 

Explicit using auto as device:

import { pipeline } from '@huggingface/transformers';

let pipe = await pipeline('sentiment-analysis', null, { device: 'auto' });

let out = await pipe('I love transformers!');
// [{'label': 'POSITIVE', 'score': 0.999817686}]

---

To solve this annoying config, the PR improves the environment support for Exposed ORT by implicitly selecting 'auto' as the default fallback instead of 'wasm'.

import { pipeline } from '@huggingface/transformers';

let pipe = await pipeline('sentiment-analysis');

let out = await pipe('I love transformers!');
// [{'label': 'POSITIVE', 'score': 0.999817686}]