Datacube-alchemist

Damien wasn't careful enough when refactoring some code, and it wasn't tested. This should fix it.

What's Changed
* Fix find-fill-missing by alexgleith in https://github.com/opendatacube/datacube-alchemist/pull/124
* Update transforms.py by erin-telfer in https://github.com/opendatacube/datacube-alchemist/pull/125
* Update transforms.py by erin-telfer in https://github.com/opendatacube/datacube-alchemist/pull/126
* Update transforms.py by erin-telfer in https://github.com/opendatacube/datacube-alchemist/pull/127

New Contributors
* erin-telfer made their first contribution in https://github.com/opendatacube/datacube-alchemist/pull/125

**Full Changelog**: https://github.com/opendatacube/datacube-alchemist/compare/0.5.9...0.6.0

1. Add cloud mask for burns transform
2. Dependency version updates and pinning
3. AWS exception handling

Update burnt area process configuration, provisional configuration, algorithm update.

* Pin xarray to 0.16.1

* Update WOfS version to `1.6.5` to include USGS C2 masking of low/high values