ui: move dropdown selection menu on top of filter dropdown

**Is your feature request related to a problem? Please describe.**

Thanks to @dongniwang for pointing this out. When opening a dropdown selection menu whose height exceeds the height of its parent filter dropdown, the selections get cut off and the user needs to scroll down using the filter dropdown.

This happens to every dropdown selection menu across cluster UI.

|Sessions Filter|
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| |

|Workload Insights Filter|
|--------------|
||

|Schema Insights Filter|
|--------------|
||

**Describe the solution you'd like**
It would be great if we moved the dropdown selection menu on top of the filter dropdown so that the user would be able to see all the options at once and would not need to scroll. See below:

|Figma Mock of solution|
|-----------------------|
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Jira issue: CRDB-23140