feat: v1 client generation

[stephaniewang526]

Fixes b/147355958

[codecov]

Codecov Report

Merging #64 into master will increase coverage by 0.98%.
The diff coverage is 71.32%.

@@             Coverage Diff              @@
##             master      #64      +/-   ##
============================================
+ Coverage     70.16%   71.15%   +0.98%     
- Complexity      184      232      +48     
============================================
  Files            28       34       +6     
  Lines          1314     1643     +329     
  Branches          3        4       +1     
============================================
+ Hits            922     1169     +247     
- Misses          389      470      +81     
- Partials          3        4       +1

Impacted Files	Coverage Δ	Complexity Δ
.../bigquery/storage/v1/BaseBigQueryReadSettings.java	21.21% <21.21%> (ø)	2 <2> (?)
...oud/bigquery/storage/v1/stub/BigQueryReadStub.java	25% <25%> (ø)	1 <1> (?)
...orage/v1/stub/GrpcBigQueryReadCallableFactory.java	37.5% <37.5%> (ø)	3 <3> (?)
...ud/bigquery/storage/v1/BaseBigQueryReadClient.java	50% <50%> (ø)	8 <8> (?)
...uery/storage/v1/stub/BigQueryReadStubSettings.java	84.67% <84.67%> (ø)	12 <12> (?)
...bigquery/storage/v1/stub/GrpcBigQueryReadStub.java	85.54% <85.54%> (ø)	9 <9> (?)
... and 14 more

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