Support custom search attributes of type Duration

[darshan-au]

Is your feature request related to a problem? Please describe.
Yes, I'm trying to add a custom search attribute that capture duration between a collection of steps in the workflow execution. These are the subset of steps that define a business usecase in my workflow execution and hence being able to filter on workflows that exceeded a threshold is important. I'm trying to create a custom search attribute that behaves similar to the default ExecutionDuration filter. Currently temporal supports creating custom search attributes of type Int or Datetime. Neither of them support my usecase of being able to apply a filter using duration strings.

Describe the solution you'd like
Add support for creating custom search attributes of type Duration that allow users to filter using duration strings like 1m, 1h or 1d etc.

Describe alternatives you've considered
Currently I'm limited to creating a custom search attribute of the type Int and using numeric filters. Using Int as the type here is limiting users from applying the correct filters.
For example: If UserA creates a custom search attribute of type Int named myCustomDuration and stores milliseconds in it. UserB won't know that they have to provide milliseconds as values for applying the numeric filter.

Being able to use search attributes of type Duration would be very useful in such cases.