fix: dashboard variables should properly load for imported dashboards

[vikrantgupta25]

Summary

• imported dashboards variables not working and showing empty data
• now since we moved to sequential approach we check for variablesToBeUpdated queue and the variable should be present in the queue to get updated.
• now even if we add the variables on the first load of dashboard it won't work as it will update all the existing values nested structure as well.
• so we only update if either present in queue or the selectedValue is not something that came in the new options.

Related Issues / PR's

fixes #5121

Screenshots

Screen.Recording.2024-05-31.at.3.51.18.PM.mov

Affected Areas and Manually Tested Areas

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[srikanthccv]

This one is tricky. I will take a look.

[srikanthccv]

LGTM. One a separate note, It would be great to have tests for small changes so that the test suite grows over the time.