[clangd] Add Hover.MacroContentsLimit config option (#155105) Currently macro expansions are hard capped at 2048. This PR adds the `Hover.MacroContentsLimit` config option for overriding the default. Fixes https://github.com/llvm/llvm-project/issues/153355 GitOrigin-RevId: a0cc776732980e792b201e3848c1049dfc3b1836