[js] changes to allow Float16Array if any polyfill is available (#19305)
### Description
This change adds only necessary code to enable ort-web works with any
Float16Array polyfill. Unlike #19302, in this PR, ort-web does not
include any specific polyfill; instead, it's user's choice for how to
use a polyfill.
ORT-web uses Float16Array if it's available; otherwise, fallback to use
Uint16Array.
```js
// case 1: user does not use polyfill:
import * as ort from 'onnxruntime-web';
const myF16Data = new Uint16Array(...); // need to use Uint16Array
const myF16tensor = new ort.Tensor('float16', myF16Data, dims);
```
```js
// case 2: user use polyfill:
import * as ort from 'onnxruntime-web';
import {
Float16Array, isFloat16Array, isTypedArray,
getFloat16, setFloat16,
f16round,
} from "@petamoriken/float16";
globalThis.Float16Array = Float16Array; // ort-web will pick the global Float16Array
const myF16Data = new Float16Array(...); // Use the polyfilled Float16Array type
const myF16tensor = new ort.Tensor('float16', myF16Data, dims);
```
onnxruntime
58f49216 - [js] changes to allow Float16Array if any polyfill is available (#19305)
