Raise ARIMA parameter limits from 4 to 8

[Nyrio]

Resolves #3915

This PR still doesn't allow arbitrary parameters (because of the Jones transform kernel that uses the parameters as a template argument in order to work with registers).
But fixing the limit to 8 instead of 4 should be enough. In most cases, the parameters don't exceed 3 or 4, and more complex models don't give better results.

I also added tests with p=5.

[tfeher]

Thanks Louis for this PR, it looks good to me.

Do I understand correctly, that one could (in theory) use the jones_transform_kernel with higher VALUE template parameter? So setting the value to 8 is not limited by the kernel resource usage, instead it is chosen so because higher values are not useful in practice?
Could you update the PR description to clarify this?

[Nyrio]

Do I understand correctly, that one could (in theory) use the jones_transform_kernel with higher VALUE template parameter? So setting the value to 8 is not limited by the kernel resource usage, instead it is chosen so because higher values are not useful in practice?

It's a bit of both. With the current implementation using a template parameter, we have to choose an arbitrary limit, and 8 should be more than enough (in practise one rarely needs more than 3 or 4)

[dantegd]

The HDBSCAN error found in CI I think is fixed now, so rerunning tests

[dantegd]

rerun tests

[dantegd]

@gpucibot merge

[codecov-commenter]

Codecov Report

❗ No coverage uploaded for pull request base (branch-21.08@bcc4cad). Click here to learn what that means.
The diff coverage is n/a.

@@               Coverage Diff               @@
##             branch-21.08    #4022   +/-   ##
===============================================
  Coverage                ?   85.59%           
===============================================
  Files                   ?      230           
  Lines                   ?    18349           
  Branches                ?        0           
===============================================
  Hits                    ?    15705           
  Misses                  ?     2644           
  Partials                ?        0           

Flag	Coverage Δ
dask	48.14% <0.00%> (?)
non-dask	77.97% <0.00%> (?)

Flags with carried forward coverage won't be shown. Click here to find out more.

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update bcc4cad...c89e677. Read the comment docs.