Added new check and fixed files with it

[m-olko]

This PR

Adds new misc-include-cleaner check for clang-tidy, and fixes all files that violated it earlier

[gemini-code-assist]

Code Review

This pull request enables the misc-include-cleaner check in .clang-tidy and cleans up header includes across various source files in the flagd provider. It also modifies numeric.cpp to use nums_res.value() instead of (*nums_res). The review feedback consistently points out that using .value() is less idiomatic, inconsistent with the rest of the file, and introduces unnecessary exception-throwing overhead since the status has already been checked. It is recommended to revert these changes to use the dereference operator * instead.

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