feat(dashboard): add multiple account support for dashboard widgets n…

[vagrawal-newrelic]

Description

Please include a summary of the change and which issue is fixed (if relevant).
Added multiple account_ids field instead of account_id field to support for multiple account id selection for dashboard nrql block in widget.
Jira story: https://new-relic.atlassian.net/browse/NR-343906

Fixes # (issue)

Type of change

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• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

Checklist:

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• My commit message follows conventional commits
• My code is formatted to Go standards
• I have performed a self-review of my own code
• I have made corresponding changes to the documentation
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes. Go here for instructions on running tests locally.

How to test this change?

Please describe how to test your changes. Include any relevant steps in the UI, HCL file(s), commands, etc

-Add a list of multiple accountIds in the account_ids field for nrql block of dashboard widget.

• perform a terraform apply
• in UI the multi-account should be selected with multiple account selected.