Dev update barra barpa varlists

[christianstassen]

I have updated the directory structure of BARRA2 and BARPA to match CORDEX-CMIP6 standards.
I also added a notebook showcasing the loading of BARRA2 data and matching BARRA2 variables with ERA5.

pytest has run successfully and the new BARRA2 tutorial notebook has been tested and runs successfully also.

[coveralls]

Pull Request Test Coverage Report for Build 18545476849

Warning: This coverage report may be inaccurate.

This pull request's base commit is no longer the HEAD commit of its target branch. This means it includes changes from outside the original pull request, including, potentially, unrelated coverage changes.

• For more information on this, see Tracking coverage changes with pull request builds.
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• For a quick fix, rebase this PR at GitHub. Your next report should be accurate.

Details

• 1 of 3 (33.33%) changed or added relevant lines in 1 file are covered.
• 25 unchanged lines in 2 files lost coverage.
• Overall coverage decreased (-0.02%) to 61.153%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
packages/data/src/pyearthtools/data/transforms/variables.py	1	3	33.33%

Files with Coverage Reduction	New Missed Lines	%
packages/data/src/pyearthtools/data/transforms/projection/init.py	5	46.15%
packages/pipeline/src/pyearthtools/pipeline/operations/xarray/join.py	20	26.15%

Totals
Change from base Build 17878657854:	-0.02%
Covered Lines:	9509
Relevant Lines:	15132

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💛 - Coveralls