Order statistics refactor

[BenjaminDev]

Description

Changes:

1. Modified the builder to handle the order-statistics (Max, Min, Median and Percentile).
2. Modified the builder to select the appropriate return types.
3. Removed the old capi files and folder and from the build file.
4. Removed the old base_percentile as there was a name clash and as far as I can see it's not DP.
5. Updated the upstream ref.
6. Added the order statistics to the python interface.
7. Updated and reinstated the tests. All tests pass (however, the CI references an older upstream ref and so the might fail there) But once checked out running pytest tests/ you should see green!

Affected Dependencies

None.

How has this been tested?

• pytest tests/ 52 passing tests.

Checklist

• I have followed the Contribution Guidelines and Code of Conduct
• I have commented my code following the OpenMined Styleguide
• I have labeled this PR with the relevant Type labels
• My changes are covered by tests