Switch eccodes python to wheelchains

[tmi]

Switching the eccodes python package to rely on wheelchain -- in particular, the wheel produced in ecmwf/eccodes#277

The changes are in short:
1/ switching the wheel build to be done in a docker with common tooling present
2/ pulling the wheel with binary eccodes at buildtime and using it for lib/include
3/ updating the findlibs call at runtime to find the right .so

What is (currently) missing:
1/ add a dep lowerbound to findlibs (ecmwf/findlibs#14 -- not released yet)
2/ switch from test pypi to real one (nothing published yet)
3/ add in full matrix over python versions, platforms, etc

[FussyDuck]

All committers have signed the CLA.

[dimbleby]

#103 (comment)

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 0% with 76 lines in your changes missing coverage. Please review.

Project coverage is 32.74%. Comparing base (23005cc) to head (43c2737).
Report is 1 commits behind head on develop.

Files with missing lines	Patch %	Lines
setup_windows.py	0.00%	44 Missing ⚠️
setup.py	0.00%	21 Missing ⚠️
gribapi/bindings.py	0.00%	11 Missing ⚠️

Additional details and impacted files

@@ Coverage Diff @@## develop #114 +/- ##
===========================================
- Coverage 33.15% 32.74% -0.41% 
===========================================
Files 16 17 +1 Lines 2645 2678 +33 Branches 190 194 +4 ===========================================
Hits 877 877 - Misses 1752 1785 +33 
Partials 16 16 

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