[test] Move CodeAssembler tests to a separate file.

src/compiler/code-assembler.h

Index: src/compiler/code-assembler.h
diff --git a/src/compiler/code-assembler.h b/src/compiler/code-assembler.h
index 033d94775535bfb5a5423b8126a51cef8f00bc97..03718755309dfd73a1bef9e18b7ad08aa7dce0cf 100644
--- a/src/compiler/code-assembler.h
+++ b/src/compiler/code-assembler.h
@@ -362,8 +362,6 @@ class CodeAssembler {
   virtual void CallEpilogue();
 
  private:
-  friend class CodeAssemblerTester;
-
   CodeAssembler(Isolate* isolate, Zone* zone, CallDescriptor* call_descriptor,
                 Code::Flags flags, const char* name);