ref/#2540-Move Search Logic from Search.execute() to FhirEngine.search()

[itstanany]

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Fixes #2540

Description
Clear and concise code change description.
I moved the search logic implementation from Search.execute to FhirEngine.search
For better separation of concerns and single responsibility principles

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Have you considered any alternatives? And if so, why have you chosen the approach in this PR?

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[jingtang10]

the code is duplicated not moved.

[jingtang10]

the code is duplicated and not moved. also, i actually feel it might be better to move this method to the search package instead of the other way around.

@MJ1998 @aditya-07 @santosh-pingle @yigit fyi