Image space cleanup for app images

Removed Heap::GetImageSpace, added Heap::GetBootImageSpace.

Generalized some logic in the class linker for image spaces.

Bug: 22858531

Change-Id: Ib3e12bb061a247e232d3dc93b0d6b35eb3a34d25
diff --git a/compiler/driver/compiler_driver.cc b/compiler/driver/compiler_driver.cc
index ecbc3a2..bf3a865 100644
--- a/compiler/driver/compiler_driver.cc
+++ b/compiler/driver/compiler_driver.cc
@@ -1552,7 +1552,7 @@
       *type = sharp_type;
     }
   } else {
-    auto* image_space = heap->GetImageSpace();
+    auto* image_space = heap->GetBootImageSpace();
     bool method_in_image = false;
     if (image_space != nullptr) {
       const auto& method_section = image_space->GetImageHeader().GetMethodsSection();