ggml-webgpu: parameterize submission size and add iOS specific limits (#21533)

ggml-webgpu: parameterize submission size and add iOS specific limits (#21533)

* Work towards removing bitcast

* Move rest of existing types over

* Add timeout back to wait and remove synchronous set_tensor/memset_tensor

* move to unpackf16 for wider compatibility

* cleanup

* Remove deadlock condition in free_bufs

* Start work on removing parameter buffer pools

* Simplify and optimize further

* simplify profile futures

* Fix stride

* Try using a single command buffer per batch

* formatting

* Add parameters for different browsers in-flight submissions

* Update handling of batch size too

* Throttle ios as much as possible

* Increase timeout for llvm-pipe testing