fix(dashboards): remove omitempty on widgets to allow creating pages with no widgets

[pranav-new-relic]

• This PR addresses a fix to an issue in the Terraform Provider : Error creating dashboard from json terraform-provider-newrelic#2376 to enable creating a dashboard with pages comprising no widgets.
• For this, omitempty has been removed next to the relevant datatype, and a test has been added to validate this change.
• For a more detailed explanation on the necessity of these changes, please see this Terraform PR: fix(dashboards): code changes to enable dashboards with empty pages terraform-provider-newrelic#2397

[codecov-commenter]

Codecov Report

Merging #1033 (7afe6a4) into main (4c18484) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main    #1033   +/-   ##
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  Coverage   41.62%   41.62%           
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  Files          79       79           
  Lines        4956     4956           
=======================================
  Hits         2063     2063           
  Misses       2745     2745           
  Partials      148      148           

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[NSSPKrishna]

@pranav-new-relic, should a comment be added to Tutone file, mentioning the avoidance of generating this specific type?

[pranav-new-relic]

@pranav-new-relic, should a comment be added to Tutone file, mentioning the avoidance of generating this specific type?

Thanks for the suggestion; I'll add a comment above these modified datatypes to not be generated/modified via tutone.