Fix LifetimeDependenceDiagnostics to ignore closure captures

ClosureLifetimeFixup now emits mark_dependence [nonescaping]. Those should be
ignored by diagnostics. In the capture case, the dependence has already been
resolved, and may not match the SIL patterns that we expect for source-level
lifetime dependencies.

Fixes rdar://125375685 ([nonescapable] Fix lifetime-dependence diagnostics in the stdlib)

(cherry picked from commit 36b9ed4)

Author: atrick

SwiftCompilerSources/Sources/Optimizer/FunctionPasses/LifetimeDependenceDiagnostics.swift

@@ -45,7 +45,7 @@ let lifetimeDependenceDiagnosticsPass = FunctionPass(
     }
   }
   for instruction in function.instructions {
-    if let markDep = instruction as? MarkDependenceInst {
+    if let markDep = instruction as? MarkDependenceInst, markDep.isUnresolved {
       if let lifetimeDep = LifetimeDependence(markDep, context) {
         analyze(dependence: lifetimeDep, context)
       }