[FIXES #12766] API for timeseries settings

[Gpetrak]

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This PR introduces an API for time-series settings while it moves the GeoServer-API logic which is included to the geonode/layers/views and geonode/layers/api/views to the GeoServer helpers. The cooresponding issue is the #12766

[codecov]

Codecov Report

Attention: Patch coverage is 31.90184% with 111 lines in your changes missing coverage. Please review.

Project coverage is 64.73%. Comparing base (91f32c6) to head (5fe9a57).

Additional details and impacted files

@@            Coverage Diff             @@
##           master   #12767      +/-   ##
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- Coverage   67.00%   64.73%   -2.27%     
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  Files         952      953       +1     
  Lines       56912    57052     +140     
  Branches     6725     6736      +11     
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- Hits        38134    36934    -1200     
- Misses      17166    18537    +1371     
+ Partials     1612     1581      -31