[js/web] Update API for `ort.env.webgpu` (#23026)
### Description
This PR is a replacement of #21671. It offers a new way for accessing
the following:
- `ort.env.webgpu.adapter`:
- **deprecating**. There is no point to get the value of it. Once
`GPUDevice.adapterInfo` is supported, there is no point to set the value
too.
- `ort.env.webgpu.device`:
- set value of `GPUDevice` if user created it. Use at user's own risk.
- get value of `Promise<GPUDevice>`. if not exist, create a new one. if
exist return it.
- `ort.env.webgpu.powerPreference`:
- **deprecating**. encouraging users to set `ort.env.webgpu.device` if
necessary.
- `ort.env.webgpu.forceFallbackAdapter`:
- **deprecating**. encouraging users to set `ort.env.webgpu.device` if
necessary.
