[js/web] fix a few package consuming problems (#18109)
### Description
This PR tries to fix a part of the NPM package consuming problems for
onnxruntime-web (ES module) as described in #10913:
- reduce the package size to fit the 150MB restriction in jsdelivr, by
removing dev build targets for uncommon exports
- add default export to support `import ort from 'onnxruntime-web';`
(currently only support `import * as ort from 'onnxruntime-web';`
