samples: Sample for configuring connection pool

[billyjacobson]

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Fixes #<issue_number_goes_here> ☕️

[snippet-bot]

Here is the summary of changes.

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• samples/snippets/src/main/java/com/example/bigtable/ConfigureConnectionPool.java:19, tag bigtable_configure_connection_pool

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[codecov]

Codecov Report

Merging #601 (2167c83) into master (8c16fa4) will increase coverage by 2.17%.
The diff coverage is n/a.

@@             Coverage Diff              @@
##             master     #601      +/-   ##
============================================
+ Coverage     81.26%   83.44%   +2.17%     
- Complexity     1129     1198      +69     
============================================
  Files           106      110       +4     
  Lines          7047     7309     +262     
  Branches        370      383      +13     
============================================
+ Hits           5727     6099     +372     
+ Misses         1121     1009     -112     
- Partials        199      201       +2     

Impacted Files	Coverage Δ	Complexity Δ
...e/cloud/bigtable/data/v2/BigtableDataSettings.java	69.44% <0.00%> (-2.39%)	8.00% <0.00%> (ø%)
...table/admin/v2/stub/BigtableInstanceAdminStub.java	3.70% <0.00%> (-0.15%)	1.00% <0.00%> (ø%)
...ogle/cloud/bigtable/data/v2/stub/BigtableStub.java	0.00% <0.00%> (ø)	0.00% <0.00%> (ø%)
.../cloud/bigtable/data/v2/stub/GrpcBigtableStub.java	0.00% <0.00%> (ø)	0.00% <0.00%> (ø%)
...bigtable/admin/v2/stub/BigtableTableAdminStub.java	3.22% <0.00%> (ø)	1.00% <0.00%> (ø%)
...table/admin/v2/BaseBigtableTableAdminSettings.java	8.75% <0.00%> (ø)	2.00% <0.00%> (ø%)
...able/data/v2/stub/GrpcBigtableCallableFactory.java	0.00% <0.00%> (ø)	0.00% <0.00%> (ø%)
...le/admin/v2/BaseBigtableInstanceAdminSettings.java	9.21% <0.00%> (ø)	2.00% <0.00%> (ø%)
...v2/stub/GrpcBigtableTableAdminCallableFactory.java	50.00% <0.00%> (ø)	4.00% <0.00%> (ø%)
...stub/GrpcBigtableInstanceAdminCallableFactory.java	50.00% <0.00%> (ø)	4.00% <0.00%> (ø%)
... and 19 more

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