use buffered channel to manage items in query pool

[asmyasnikov]

Pull request type

Please check the type of change your PR introduces:

• Bugfix
• Feature
• Code style update (formatting, renaming)
• Refactoring (no functional changes, no api changes)
• Build related changes
• Documentation content changes
• Other (please describe):

What is the current behavior?

Issue Number: N/A

What is the new behavior?

Other information

[github-actions]

summary

Base version: v3.74.6-0.20240704085220-890206eacaa7 (master)
Cannot suggest a release version.
Can only suggest a release version when compared against the most recent version of this major: v3.74.5.

[github-actions]

🌋 Here are results of SLO test for Native ydb-go-sdk/v3 over table-service:

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[github-actions]

🌋 Here are results of SLO test for Go SDK database/sql:

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[github-actions]

🌋 Here are results of SLO test for Go SDK xorm:

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[github-actions]

🌋 Here are results of SLO test for Native ydb-go-sdk/v3 over query-service:

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[github-actions]

🌋 Here are results of SLO test for Native ydb-go-sdk/v3 over query-service with session pool:

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[github-actions]

🌋 Here are results of SLO test for Go SDK gorm:

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[codecov-commenter]

Codecov Report

❌ Patch coverage is 93.81443% with 6 lines in your changes missing coverage. Please review.
✅ Project coverage is 41.73%. Comparing base (890206e) to head (a78bced).
⚠️ Report is 1615 commits behind head on master.

Files with missing lines	Patch %	Lines
internal/pool/pool.go	93.81%	6 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1320   +/-   ##
=======================================
  Coverage   41.73%   41.73%           
=======================================
  Files         321      321           
  Lines       34050    34073   +23     
=======================================
+ Hits        14211    14222   +11     
- Misses      19371    19379    +8     
- Partials      468      472    +4     

Flag	Coverage Δ
go-1.20.x	44.02% <93.81%> (-0.02%)	⬇️
go-1.21.x	44.03% <93.81%> (-0.03%)	⬇️
go-1.22.x	41.70% <93.81%> (+<0.01%)	⬆️
macOS	41.25% <92.77%> (+0.04%)	⬆️
ubuntu	41.22% <92.77%> (-0.01%)	⬇️
unit	41.73% <93.81%> (+<0.01%)	⬆️
windows	41.71% <93.81%> (-0.01%)	⬇️

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