[TypeChecker] Avoid checking lazy property accessors if they haven't been synthesized yet

Ttheir availability is going to match the property itself.
This is a workaround for lazy type-checking because synthesis
of accessors for such properties requires a reference to
`self` which won't be available because pattern binding
for the variable was skipped.

Resolves: rdar://129359362
Resolves: rdar://159463230
Resolves: https://github.com/swiftlang/swift/issues/84041

test/Inputs/lazy_typecheck.swift

@@ -402,3 +402,7 @@ extension PublicStruct {
     lhs = rhs
   }
 }
+
+public class LazyPropertyWithClosureType {
+  public lazy var lazyVar: Int = { 2 }()
+}

test/Inputs/lazy_typecheck_client.swift

@@ -142,3 +142,8 @@ func testOperators() {
   var a: PublicStruct
   a <<< PublicStruct(x: 2)
 }
+
+func testLazyPropertyWithInitClosureReference(t: LazyPropertyWithClosureType) {
+  _ = t.lazyVar
+  t.lazyVar = 42
+}