Add getFileInfoObject API in gcsio

[singhravidutt]

Adding a new API getFileInfoObject. It differs from getFileInfo in following cases

1. getFileInfo provides the info even for a directory, getFileInfoObject will only provide valid responses if provided path is a valid gcs object.
2. getFileInfo makes two parallel calls to listObject and getItemInfo where as getFileInfoObject will only make a call to getItemInfo.

This API will hep in extracting fileInfo where we know for sure that request path is an object and not a directory. Having this knowledge will be cost effective as we will be avoiding a class 'A' operation i.e. listObject call.

[singhravidutt]

/gcbrun

[codecov]

Codecov Report

Attention: Patch coverage is 87.50000% with 1 lines in your changes are missing coverage. Please review.

Project coverage is 81.82%. Comparing base (f39c78f) to head (2e3a4d1).

Files	Patch %	Lines
...hadoop/gcsio/GoogleCloudStorageFileSystemImpl.java	87.50%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff            @@
##             master    #1160   +/-   ##
=========================================
  Coverage     81.81%   81.82%           
- Complexity     1901     1903    +2     
=========================================
  Files           103      103           
  Lines          8397     8405    +8     
  Branches       1027     1028    +1     
=========================================
+ Hits           6870     6877    +7     
  Misses         1105     1105           
- Partials        422      423    +1     

Flag	Coverage Δ
integrationtest	68.54% <87.50%> (+0.06%)	⬆️
unittest	73.37% <87.50%> (+0.01%)	⬆️

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