[DE-664] Deprecating Batch API

[apetenchea]

https://www.arangodb.com/docs/stable/http/batch-request.html

• The batch API is deprecated since ArangoDB 3.8.0 and will be removed in a future version.
• The BatchDatabase is still available, but it now uses a TreadPoolExecutor internally.
• For backwards compatibility, the BatchDatabase uses only one worker thread, essentially sending the requests sequentially. Feel free to set the max_workers parameter to a higher value if you want to use multiple threads, but be aware that the requests will be sent in parallel, which may cause problems if you are using transactions.
• To discourage the use of this API, we now issue a warning when the BatchDatabase is used. This warning may be disabled by the user.

Note that {"foo": "bar"} may be inserted after {"foo": "baz"} in the following example:

with db.begin_batch_execution(max_workers=2) as batch_db:
    job1 = batch_db.collection.insert({"foo": "bar"})
    job2 = batch_db.collection.insert({"foo": "baz"})

Documentation has been updated accordingly.

[apetenchea]

Note that this test no longer makes sense with the current implementation, because we don't throw this exception anymore.

[codecov-commenter]

Codecov Report

Merging #279 (3752307) into main (744a6e9) will decrease coverage by 0.38%.
Report is 12 commits behind head on main.
The diff coverage is 93.54%.

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@@            Coverage Diff             @@
##             main     #279      +/-   ##
==========================================
- Coverage   99.01%   98.64%   -0.38%     
==========================================
  Files          26       26              
  Lines        3958     3981      +23     
==========================================
+ Hits         3919     3927       +8     
- Misses         39       54      +15     

Files Changed	Coverage Δ
arango/client.py	98.41% <ø> (ø)
arango/http.py	100.00% <ø> (ø)
arango/collection.py	97.59% <91.39%> (-0.92%)	⬇️
arango/database.py	99.72% <100.00%> (-0.14%)	⬇️
arango/exceptions.py	100.00% <100.00%> (ø)
arango/executor.py	99.35% <100.00%> (-0.13%)	⬇️
arango/job.py	100.00% <100.00%> (ø)
arango/request.py	94.44% <100.00%> (ø)
arango/utils.py	87.50% <100.00%> (-12.50%)	⬇️

[aMahanna]

LGTM