Tensor Dim, support Dim.capacity > max(Dim.dyn_size_ext)

[albertz]

Currently, in multiple places (where exactly?) we have the assumption, for some tensor x: Tensor that max(x.dims[i].dyn_size_ext.raw_tensor) == x.raw_tensor.shape[i].

We want to support the case where max(x.dims[i].dyn_size_ext.raw_tensor) < x.raw_tensor.shape[i]. Specifically, we always have x.dims[i].capacity == x.raw_tensor.shape[i], thus we want to support the case dim.capacity > max(dim.dyn_size_ext.raw_tensor).

This is e.g. needed for JAX, where we only can have static shapes. So there we would compile our code for a few predefined batch sizes (fixed batch_dim, fixed spatial dim), and then the batching would prepare the batch fitting for one of these predefined sizes (e.g. via bucketing). But this often means that we don't reach the max possible seq len for this batch.