Add decompress module for prototype cupy backend

[GarethCabournDavies]

For the CuPy backend, we need the decompress module translated; this is that translation

Standard information about the request

This is a new feature
This change affects the offline search, as I don't think any others (use compressed waveforms)
This change changes scientific output
This change follows style guidelines (See e.g. PEP8), has been proposed using the contribution guidelines
This change will require additional dependencies (CuPy in the new backend)

Contents

This is effectively a copy of the decompress_cuda module, but using cupy rather than pycuda

Links to any issues or associated PRs

#4952

Testing performed

Comparison of waveforms with/without compression and from CPU/CuPy:

• The author of this pull request confirms they will adhere to the code of conduct

[GarethCabournDavies]

Testing

mismatches:

CuPy Not Compressed -- CuPy Compressed [0.00122166]
CuPy Not Compressed -- CPU Not Compressed [1.7881393e-07]
CuPy Not Compressed -- CPU Compressed [0.00122166]
CuPy Compressed -- CPU Not Compressed [2.8014183e-05]
CuPy Compressed -- CPU Compressed [0.]
CPU Not Compressed -- CPU Compressed [0.00122112]

This means that the compressed waveform implementation on CPU and CuPy is exactly the same

[spxiwh]

(@GarethCabournDavies You will need to wait for #4962 to be merged before sanity tests could pass here, or at least you'll need fixes in there (like for documentation build). I'll hold on reviewing this until #4962 is merged)

[spxiwh]

Is this synchronize needed?

[spxiwh]

Can't this be easily supported now with dynamic types in Cupy?

[spxiwh]

Some minor comments, but I'd be happy to merge this once the tests pass.