[DE-542] Adding support for shards retrieval

[apetenchea]

Main changes

• Adding shards() method to Collection, reflecting /_api/collection/{collection-name}/shards. It will be available only in a cluster setup.

Minor patches

• Adding docstring for computed_values
• Updating driver version in request header
• Fixing test_database_misc_methods. Getting and setting log levels for individual servers is available only in a cluster.

[codecov-commenter]

Codecov Report

Merging #274 (410164c) into main (744a6e9) will decrease coverage by 0.18%.
Report is 8 commits behind head on main.
The diff coverage is 64.70%.

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@@ Coverage Diff @@ ## main #274 +/- ## ========================================== - Coverage 99.01% 98.84% -0.18%  ========================================== Files 26 26 Lines 3958 3970 +12 ========================================== + Hits 3919 3924 +5  - Misses 39 46 +7 

Files Changed	Coverage Δ
arango/client.py	98.41% <ø> (ø)
arango/http.py	100.00% <ø> (ø)
arango/collection.py	97.84% <60.00%> (-0.67%)	⬇️
arango/exceptions.py	100.00% <100.00%> (ø)
arango/request.py	94.44% <100.00%> (ø)

... and 1 file with indirect coverage changes