[RemoteInspection] Factor out buildContextDescriptorManglingForSymbol

A previous commit introduced the usage of buildContextManglingForSymbol
in buildContextDescriptorMangling, which was not quite correct, since
type nodes needed extra handling, which was done in the other version of
buildContextDescriptorMangling. This patch factors out the handling of
building context descriptors mangling from symbols, and updates both
call sites to use the new function instead.

rdar://165950673
(cherry picked from commit ab507be)

Author: augusto2112

include/swift/Remote/MetadataReader.h

@@ -2659,6 +2659,26 @@ class MetadataReader {
     return resultAddress;
   }
 
+  Demangle::NodePointer
+  buildContextDescriptorManglingForSymbol(llvm::StringRef symbol,
+                                          Demangler &dem) {
+    if (auto demangledSymbol = buildContextManglingForSymbol(symbol, dem)) {
+      // Look through Type nodes since we're building up a mangling here.
+      if (demangledSymbol->getKind() == Demangle::Node::Kind::Type) {
+        demangledSymbol = demangledSymbol->getChild(0);
+      }
+      return demangledSymbol;
+    }
+
+    return nullptr;
+  }
+
+  Demangle::NodePointer
+  buildContextDescriptorManglingForSymbol(const std::string &symbol,
+                                          Demangler &dem) {
+    return buildContextDescriptorManglingForSymbol(dem.copyString(symbol), dem);
+  }
+
   Demangle::NodePointer
   buildContextDescriptorMangling(const ParentContextDescriptorRef &descriptor,
                                  Demangler &dem, int recursion_limit) {
@@ -2672,15 +2692,7 @@ class MetadataReader {
 
     // Try to demangle the symbol name to figure out what context it would
     // point to.
-    auto demangledSymbol = buildContextManglingForSymbol(descriptor.getSymbol(),
-                                                         dem);
-    if (!demangledSymbol)
-      return nullptr;
-    // Look through Type notes since we're building up a mangling here.
-    if (demangledSymbol->getKind() == Demangle::Node::Kind::Type){
-      demangledSymbol = demangledSymbol->getChild(0);
-    }
-    return demangledSymbol;
+    return buildContextDescriptorManglingForSymbol(descriptor.getSymbol(), dem);
   }
 
   Demangle::NodePointer
@@ -2696,7 +2708,7 @@ class MetadataReader {
             Reader->resolvePointerAsSymbol(descriptor.getRemoteAddress())) {
       auto symbol = remoteAbsolutePointer->getSymbol();
       if (!symbol.empty()) {
-        if (auto demangledSymbol = buildContextManglingForSymbol(symbol, dem)) {
+        if (auto demangledSymbol = buildContextDescriptorManglingForSymbol(symbol, dem)) {
           return demangledSymbol;
         }
       }