[clang] [analyzer] Enforce not making overly complicated symbols (PR #144327)

[Donát Nagy via cfe-commits]

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@@ -46,7 +50,7 @@ class SymbolRegionValue : public SymbolData {
 
   friend class SymExprAllocator;
   SymbolRegionValue(SymbolID sym, const TypedValueRegion *r)
-      : SymbolData(SymbolRegionValueKind, sym), R(r) {
+      : SymbolData(ClassKind, sym), R(r) {
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NagyDonat wrote:

What is the reason for refactoring the internal machinery of the `classof()` methods? Does the rest of this commit depend on these changes?

As both these changes and the rest of the commit are large, I feel that perhaps it would be better to put these into a separate NFC change, but I can understand and accept if you don't want to bother with the rebasing. 

https://github.com/llvm/llvm-project/pull/144327