support otlp_grpc alias for otlp exporter

[mbaykara]

Link to tracking issue

Fixes #14099

[codecov]

Codecov Report

❌ Patch coverage is 96.29630% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 92.24%. Comparing base (5adc149) to head (b40473c).

Files with missing lines	Patch %	Lines
exporter/otlpexporter/factory.go	96.29%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #14165      +/-   ##
==========================================
- Coverage   92.25%   92.24%   -0.02%     
==========================================
  Files         658      658              
  Lines       41186    41213      +27     
==========================================
+ Hits        37998    38018      +20     
- Misses       2182     2187       +5     
- Partials     1006     1008       +2     

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