Refactor MemMap::MapAnonymous().

Remove the address argument from the shortcut overload and
introduce one more shortcut overload. This makes it easier
to find all uses where we pass non-null address hint.

Remove `requested_begin` parameter from some constructors
where we were always passing null. Rewrite some tests to
use the reservation API.

Test: m test-art-host-gtest
Test: testrunner.py --host --optimizing
Bug: 118408378
Change-Id: Ibbbb96667e7cc11cf7fea119892463d8dbc9a8b5
diff --git a/compiler/common_compiler_test.cc b/compiler/common_compiler_test.cc
index 586891a..fc8cd52 100644
--- a/compiler/common_compiler_test.cc
+++ b/compiler/common_compiler_test.cc
@@ -328,6 +328,8 @@
                                             (size_t)120 * 1024 * 1024,  // 120MB
                                             PROT_NONE,
                                             false /* no need for 4gb flag with fixed mmap */,
+                                            /*reuse=*/ false,
+                                            /*reservation=*/ nullptr,
                                             &error_msg);
   CHECK(image_reservation_.IsValid()) << error_msg;
 }