[clang-tools-extra] [clangd] Add `HeaderInsertion` yaml config option (PR #128503)

[Nathan Ridge via cfe-commits]

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@@ -668,6 +668,7 @@ class FlagsConfigProvider : public config::Provider {
     std::optional<Config::ExternalIndexSpec> IndexSpec;
     std::optional<Config::BackgroundPolicy> BGPolicy;
     std::optional<Config::ArgumentListsPolicy> ArgumentLists;
+    std::optional<Config::HeaderInsertionPolicy> _HeaderInsertion;
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HighCommander4 wrote:

nit: I haven't seen this convention (using an underscore to avoid a name conflict) used elsewhere in the clangd code, so let's not use it here. We can e.g. call the variable `HeaderInsertionPolicy` instead.

https://github.com/llvm/llvm-project/pull/128503