### Description
<!-- Describe your changes. -->
Switch to setImmediate to avoid starving the Node.js event loop
There should really be a true async version though, running
computationally intensive things on the event loop will stop everything
else from happening while it is running, e.g. a web server from
answering requests.
This can be done by wrapping `RunAsync` behind a
[`napi::Promise`](https://github.com/nodejs/node-addon-api/blob/main/doc/promises.md)
to run on the onnxruntime thread pool or [`AsyncWorker`](
https://github.com/nodejs/node-addon-api/blob/main/doc/async_worker.md)
for the Node.js/libuv thread pool.
### Motivation and Context
<!-- - Why is this change required? What problem does it solve?
- If it fixes an open issue, please link to the issue here. -->
Without this, if you run inference in a tight loop, without anything
else in between that is async/deferred, `process.nextTick` will lead to
starving the event loop and not letting anything else run,
`setImmediate` at least lets the event loop spin between calls to `run`.
See
https://dev.to/ynmanware/setimmediate-settimeout-and-process-nexttick-3mfd
Contributed on behalf of [Swimm](https://swimm.io/)
### Description
Following the design document:
* Added CreateTrainingSessionHandler to the Backend interface
* All existing Backend implementations throw an error for the new method
createTrainingSessionHandler
* Created TrainingSession namespace, interface, and
TrainingSessionFactory interface
* Created TrainingSessionImpl class implementation
As methods are implemented, the TrainingSession interface will be added
to or modified.
### Motivation and Context
Adding the public-facing interfaces to the onnxruntime-common package is
one of the first steps to support ORT training for web bindings.
---------
Co-authored-by: Caroline Zhu <carolinezhu@microsoft.com>
* working on re-organizing js code for ortweb
* remove dup files
* move folder
* fix common references
* fix common es5
* add webpack to common
* split interfact/impl
* use cjs for node
* add npmignore for common
* update sourcemap config for common
* update node
* adjust folder/path in CI and build
* update folder
* nit: readme
* add bundle for dev
* correct nodejs paths
* enable ORT_API_MANUAL_INIT
* set name for umd library
* correct name for commonjs export
* add priority into registerBackend()
* fix npm ci pwd
* update eslintrc
* revise code
* revert package-lock lockfileVersion 2->1
* update prebuild
* resolve comments
* update document
* revise eslint config
* update eslint for typescript rules
* revert changes by mistake in backend.ts
* add env
* resolve comments
