Speed up Python GraphBinary deserialization (3.7)

[kirill-stepanishin]

The GraphBinary reader built a DataType enum member from the type byte for every object it decoded. That per-object enum construction heavily degrades deserialization performance on large result sets.

The reader now builds a {type code: deserializer} lookup table once up front and dispatches on the raw integer instead, avoiding per-object enum construction. Behavior is unchanged: an unknown type code still raises ValueError("... is not a valid DataType").

Performance

Benchmarked on two cross-region EC2 instances (server in US-EAST-2, client in US-WEST-2) to capture realistic network latency, against the Modern graph over WebSocket on Python 3.11. Each query was run with and without this change, alternating back to back across 3 sweeps, reporting the median.

Query	Before	After	Change
g.V().repeat(both()).times(12) (~200k results)	6.81 s	5.36 s	21% faster
g.V() (6 results)	0.181 s	0.181 s	no change

The improvement is significant on large result sets, where per-object deserialization cost dominates, and scales with the number of objects returned.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 75.52%. Comparing base (4722890) to head (d4e2af1).
⚠️ Report is 14 commits behind head on 3.7-dev.

Additional details and impacted files

@@              Coverage Diff              @@
##             3.7-dev    #3504      +/-   ##
=============================================
+ Coverage      75.49%   75.52%   +0.02%     
- Complexity     13161    13175      +14     
=============================================
  Files           1092     1093       +1     
  Lines          67208    67226      +18     
  Branches        7391     7396       +5     
=============================================
+ Hits           50742    50770      +28     
+ Misses         13837    13833       -4     
+ Partials        2629     2623       -6     

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.