Clang-tidy eliminate unused parts of headers

[tschuett]

There is/will be an include cleaner that tells you which includes you don’t need:

[RFC] Lifting "include cleaner" (missing/unused include detection) out of clangd

clangd has a feature to warn when you #include headers but don’t use them. [image] It works well (it’s still off by default, but we’re planning to turn it on soon). We’re also planning to add a warning when you use a symbol are missing #include. Together these provide analysis similar to the include-what-you-use tool, with some differences[1]. We’ve had several requests to make this available for reuse: @serge-sans-paille has been cleaning up LLVM and wants better tools. D121593 On the…