feat: add forEachDecl for LCNF

src/Lean/Compiler/LCNF/PhaseExt.lean

@@ -54,4 +54,11 @@ def getDecl? (declName : Name) : CompilerM (Option Decl) := do
 def saveBase : Pass :=
   .mkPerDeclaration `saveBase (fun decl => do decl.saveBase; return decl) .base
 
+def forEachDecl (f : Decl → CoreM Unit) : CoreM Unit := do
+  let env ← getEnv
+  for modIdx in [:env.allImportedModuleNames.size] do
+    for decl in baseExt.getModuleEntries env modIdx do
+      f decl
+  baseExt.getState env |>.forM fun _ decl => f decl
+
 end Lean.Compiler.LCNF