Changed the scope of BULK_COPY_OPERATION_CACHE to connection.

[machavan]

Description:

The BULK_COPY_OPERATION_CACHE should be defined at connection scope and not global scope to avoid incorrect cache hits across connections and potential OOM issues.

Testing:

• Updated existing unit tests for this functionality accordingly.
• Existing unit tests as part of build pass with the change.

[codecov]

Codecov Report

Attention: Patch coverage is 87.50000% with 1 line in your changes missing coverage. Please review.

Project coverage is 51.50%. Comparing base (c01814b) to head (4e78875).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
.../microsoft/sqlserver/jdbc/SQLServerConnection.java	75.00%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #2594      +/-   ##
============================================
+ Coverage     51.49%   51.50%   +0.01%     
+ Complexity     3993     3992       -1     
============================================
  Files           147      147              
  Lines         33690    33694       +4     
  Branches       5629     5630       +1     
============================================
+ Hits          17348    17355       +7     
+ Misses        13902    13882      -20     
- Partials       2440     2457      +17     

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[mmimica]

More importantly, it solves a problem when a driver instance is used to connect to different SQLServers. Tables from different databases could end up in the same static cache.

[machavan]

ADO tests are good for this PR