PHP streaming retry and exception tests

[michaelbausor]

This PR:

• Removes retry settings from PHP streaming methods. Retrying does not make sense in that context, and GAX prevents the use of retry settings for streaming methods in PHP
• Changes from INTERNAL errors to DATA_LOSS errors, because some methods are configured to retry on INTERNAL errors(!)
• Call getReceivedCalls in exception tests so that the stub will be exhausted

[codecov-io]

Codecov Report

Merging #1306 into master will decrease coverage by <.01%.
The diff coverage is 80%.

@@             Coverage Diff              @@
##             master    #1306      +/-   ##
============================================
- Coverage     86.52%   86.51%   -0.01%     
- Complexity     3816     3821       +5     
============================================
  Files           376      377       +1     
  Lines         15260    15264       +4     
  Branches       1688     1688              
============================================
+ Hits          13203    13206       +3     
  Misses         1609     1609              
- Partials        448      449       +1

Impacted Files	Coverage Δ	Complexity Δ
...main/java/com/google/api/codegen/GapicContext.java	63.41% <100%> (+0.91%)	12 <1> (+1)	⬆️
...le/api/codegen/gapic/MainGapicProviderFactory.java	94.23% <100%> (ø)	16 <0> (ø)	⬇️
.../clientconfig/php/PhpClientConfigGapicContext.java	66.66% <66.66%> (ø)	4 <4> (?)

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[garrettjonesgoogle]

LGTM