[web/js] need for more methods on tensor object

[guschmue]

original mentioned here: #17167

Methods that are commonly used by users are here:
https://github.com/xenova/transformers.js/blob/main/src/utils/tensor.js
and here:
https://github.com/dakenf/stable-diffusion-webgpu-minimal/blob/main/src/lib/Tensor.ts

We will take a look what can be done.

fyi @dakenf, @fs-eire, @xenova

[dakenf]

Maybe worth mentioning that i thought JS operations with tensors are slow but sampling for stable diffusion takes about 10ms with this code https://github.com/dakenf/stable-diffusion-webgpu-minimal/blob/main/src/lib/schedulers/PNDMScheduler.ts

I haven't measured time spent to download the result from GPU, pass it back to JS and then upload back, so keeping tensors on GPU might be a good idea. But not sure if it's worth the effort though