Remove unused headers

[kingcrimsontianyu]

This PR removes unused headers.

[bdice]

Do we need <stdexcept> for std::runtime_error?

[kingcrimsontianyu]

Thanks. Done.

[bdice]

<memory> is needed for std::unique_ptr.

[kingcrimsontianyu]

The header file remote_handle.hpp has already included <memory> for the unique pointers used in the header.

[vuule]

IIUC, we should include all used headers, regardless of redundancy with what the included headers include themselves.

[kingcrimsontianyu]

The headers I removed were reported by the clangd plug-in that comes with the dev container. The plug-in uses the "include cleaner" to identify the unused include. Given that transitive include is discouraged, and that we do not have misc-include-cleaner in the .clang-tidy file, I'll revert the changes.
Edit: I'm still seeing some of the warnings clangd makes.

[bdice]

Yes, we aim to avoid relying on transitive header inclusions. If an identifier is used in a file, the corresponding header should be included.

[bdice]

That said, I am happy to accept partial fixes that improve the state of things. For cleanups like this, it is easy to let work drag on. I prefer to accept improvements as-is even if they don’t fix every instance of a problem. Then future diffs can be smaller and we avoid generating conflicts along the way.

[kingcrimsontianyu]

Running clang-tidy with misc-include-cleaner on, it turns out quite a number of places rely on transitive include. Further changes would be necessary to fully follow the best practices.