[Image Classification] Measure the performance of session.run() in ORT rather than classifier() of Transformer.js

[ibelem]

This Image Classification demo is based on Transformer.js, which experimentally enabled WebNN by modifying some source code of Transformer.js.

const classifier = await pipeline('image-classification', modelPath, options);
const url = 'tiger.jpg';
const output = await classifier(url);

Image Classification:

1. Swapped the original perf.html and index.html
2. Removed the new perf.html

• Now the index.html will measure the performance of session.run() in ORT, the same as other demos.
• The index.html will not measure the performance of Transformer.js classifier() function anymore.
• User can change the test run numbers as usual.

@Adele101 PTAL

[ibelem]

Thanks @fdwr 's review, nearly all the format issues have been fixed. PTAL