feat: Support building a BigQueryWriteClient within the StreamWriterV2

[yayi-google]

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Fixes #<issue_number_goes_here> ☕️

[codecov]

Codecov Report

Merging #876 (0a7324a) into master (854c81e) will increase coverage by 4.53%.
The diff coverage is 94.11%.

@@             Coverage Diff              @@
##             master     #876      +/-   ##
============================================
+ Coverage     76.32%   80.85%   +4.53%     
- Complexity      967     1014      +47     
============================================
  Files            76       76              
  Lines          4156     5500    +1344     
  Branches        368      423      +55     
============================================
+ Hits           3172     4447    +1275     
- Misses          814      880      +66     
- Partials        170      173       +3     

Impacted Files	Coverage Δ	Complexity Δ
...cloud/bigquery/storage/v1beta2/StreamWriterV2.java	95.76% <94.11%> (-1.32%)	32.00 <1.00> (+3.00)	⬇️
.../cloud/bigquery/storage/v1alpha2/DirectWriter.java	77.55% <0.00%> (-1.52%)	6.00% <0.00%> (ø%)
...y/storage/v1beta1/BaseBigQueryStorageSettings.java	18.42% <0.00%> (-1.03%)	2.00% <0.00%> (ø%)
...loud/bigquery/storage/v1/BigQueryReadSettings.java	23.52% <0.00%> (-0.72%)	3.00% <0.00%> (ø%)
...bigquery/storage/v1beta2/BigQueryReadSettings.java	23.52% <0.00%> (-0.72%)	3.00% <0.00%> (ø%)
...igquery/storage/v1beta2/BigQueryWriteSettings.java	25.64% <0.00%> (-0.68%)	5.00% <0.00%> (ø%)
...gquery/storage/v1alpha2/BigQueryWriteSettings.java	25.64% <0.00%> (-0.68%)	5.00% <0.00%> (ø%)
.../bigquery/storage/v1/BaseBigQueryReadSettings.java	21.21% <0.00%> (-0.67%)	2.00% <0.00%> (ø%)
...uery/storage/v1beta2/BaseBigQueryReadSettings.java	21.21% <0.00%> (-0.67%)	2.00% <0.00%> (ø%)
...query/storage/v1beta1/BigQueryStorageSettings.java	21.05% <0.00%> (-0.57%)	3.00% <0.00%> (ø%)
... and 52 more

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