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 51.21%. Comparing base (08cd6fd) to head (6779332).
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     51.22%   51.21%   -0.01%     
- Complexity     3953     3960       +7     
============================================
  Files           147      147              
  Lines         33657    33661       +4     
  Branches       5624     5625       +1     
============================================
  Hits          17241    17241              
- Misses        13999    14004       +5     
+ Partials       2417     2416       -1     

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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.