[clang] [analyzer][NFC] Add some docs for LazyCompoundValue (PR #97407)

[Balazs Benics via cfe-commits]

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@@ -326,6 +326,12 @@ class LocAsInteger : public NonLoc {
   static bool classof(SVal V) { return V.getKind() == LocAsIntegerKind; }
 };
 
+/// The simplest example of a concrete compound value is nonloc::CompoundVal,
+/// which represents a concrete r-value of an initializer-list or a string.
+/// Internally, it contains an llvm::ImmutableList of SVal's stored inside the
+/// literal.
+///
+/// Source: https://github.com/haoNoQ/clang-analyzer-guide, v0.1, section 5.3.2.
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steakhal wrote:

If we want to phase out the guide, I don't think it's valuable to mention it here.
If you insist, let's mention this additional resource in the dev docs, but not directly here.

https://github.com/llvm/llvm-project/pull/97407