added class for get file system statistics.

[doronzuk]

added class to support request for DescribeFileSystemStatistics.
this is supported in openAPI but is not implemented in any of the SDKs

[codecov-io]

Codecov Report

❗ No coverage uploaded for pull request base (master@6e548b8). Click here to learn what that means.
The diff coverage is n/a.

@@            Coverage Diff            @@
##             master     #315   +/-   ##
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  Coverage          ?   43.49%           
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  Files             ?      141           
  Lines             ?     9784           
  Branches          ?     1553           
=========================================
  Hits              ?     4256           
  Misses            ?     5248           
  Partials          ?      280

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[CLAassistant]

All committers have signed the CLA.

[doronzuk]

@samuelchen, @suzaku can you please take a look, only missing 2 reviewers

[suzaku]

LGTM

[samuelchen]

OK to me

[doronzuk]

@samuelchen , @suzaku so we have 2 reviews? can we merge?

[JacksonTian]

The code was auto-generated, next time will overwrite your commits. I will notice the NAS team to update the SDK.