SNOW-1714154 query_tag vs Pool docs

[sfc-gh-dszmolka]

Description

This is a doc-only change, to raise awareness how Pooling works to help avoid situations like #1034

• add entry in Pooling docs to make a bit more expressed how it interacts with QUERY_TAG (and anything else which changes the Connection String, really)
• linked an example to how to add QUERY_TAG outside of the Connection String (without changing it), using SnowflakeDbCommand.QueryTag

kudos to @sfc-gh-dstempniak

Checklist

• Code compiles correctly
• Code is formatted according to Coding Conventions
• Created tests which fail without the change (if possible)
• All tests passing (dotnet test)
• Extended the README / documentation, if necessary
• Provide JIRA issue id (if possible) or GitHub issue id in PR name

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 85.80%. Comparing base (717a804) to head (c1d8031).

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1035      +/-   ##
==========================================
+ Coverage   85.79%   85.80%   +0.01%     
==========================================
  Files         118      118              
  Lines       11451    11451              
  Branches     1146     1146              
==========================================
+ Hits         9824     9826       +2     
+ Misses       1343     1342       -1     
+ Partials      284      283       -1     

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