CXX-3222 add UBSan coverage with extra alignment and fix extended alignment issues (#1329)

* Add UBSan coverage with extra alignment
* Add bsoncxx::aligned_object<T>
* Avoid leaking extended alignment requirements to parent objects
* Replace std::aligned_storage with alignas + sizeof
* Address -Walign-mismatch warnings for bson_t* returned by test_util::mock
* Address -Walign-mismatch warnings for bson_t* passed by stack<T, size>::emplace_back
* Add -static-libsan when compiling UBSan tasks with static libs

Author: eramongodb

.evergreen/config_generator/components/sanitizers.py

@@ -22,8 +22,7 @@
 # pylint: disable=line-too-long
 # fmt: off
 MATRIX = [
-    ('rhel80', ['asan',        ], ['shared', 'static'], [False, True], ['4.0', '8.0', 'latest'], ['single', 'replica', 'sharded']),
-    ('rhel80', [        'ubsan'], [          'static'], [False      ], ['4.0', '8.0', 'latest'], ['single', 'replica', 'sharded']),
+    ('rhel80', ['asan', 'ubsan'], ['shared', 'static'], [False, True], ['4.0', '8.0', 'latest'], ['single', 'replica', 'sharded']),
 ]
 # fmt: on
 # pylint: enable=line-too-long
@@ -101,7 +100,7 @@ def tasks():
                     test_vars |= {
                         'TEST_WITH_UBSAN': 'ON',
                         'example_projects_cxxflags': '-fsanitize=undefined -fno-sanitize-recover=undefined -fno-omit-frame-pointer',
-                        'example_projects_ldflags': '-fsanitize=undefined -fno-sanitize-recover=undefined',
+                        'example_projects_ldflags': '-fsanitize=undefined -fno-sanitize-recover=undefined' + (' -static-libsan' if link_type == 'static' else ''),
                     }
 
             commands += [