perf: precise cache for expr_eq_fn

We also add `m_check_set` flag for controlling whether `check_cache`
should also inspect set of hashconsed objects or not.

src/Lean/Compiler/IR/EmitC.lean

@@ -94,10 +94,7 @@ def emitCInitName (n : Name) : M Unit :=
 def shouldExport (n : Name) : Bool :=
   -- HACK: exclude symbols very unlikely to be used by the interpreter or other consumers of
   -- libleanshared to avoid Windows symbol limit
-  !(`Lean.Compiler.LCNF).isPrefixOf n &&
-  !(`Lean.IR).isPrefixOf n &&
-  -- Lean.Server.findModuleRefs is used in Verso
-  (!(`Lean.Server).isPrefixOf n || n == `Lean.Server.findModuleRefs)
+  !(`Lean.Compiler.LCNF).isPrefixOf n && !(`Lean.IR).isPrefixOf n && !(`Lean.Server).isPrefixOf n
 
 def emitFnDeclAux (decl : Decl) (cppBaseName : String) (isExternal : Bool) : M Unit := do
   let ps := decl.params