fix: restore consistency_level int in CollectionSchema.dict(), add name alias

[pymilvus-bot]

PR #3409 changed CollectionSchema.dict() to emit consistency_level as
the human-readable string (ConsistencyLevel.Name(...)) instead of its
historical int, breaking public-API back-compat for callers that
indexed dict()["consistency_level"] expecting an int — including the
milvus e2e test_milvus_client_search_query_default.

This restores the int shape and exposes the name under a new
consistency_level_name key. Callers who want the human-readable form
read the new key; existing callers stay unbroken.

See also: #2985

[sre-ci-robot]

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.85%. Comparing base (a9b5441) to head (87b8509).

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #3441   +/-   ##
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  Coverage   90.85%   90.85%           
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  Files          64       64           
  Lines       13978    13978           
=======================================
  Hits        12700    12700           
  Misses       1278     1278           

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