[clang] [analyzer] Turn NodeBuilderContext into a class (PR #84638)

[Balazs Benics via cfe-commits]

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@@ -194,11 +194,12 @@ class CoreEngine {
 };
 
 // TODO: Turn into a class.
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steakhal wrote:

Remove this TODO, as its completed.

https://github.com/llvm/llvm-project/pull/84638