Implement memtagMode and nativeHeapZeroInit manifest attrs.

memtagMode allows an app to opt in to MTE in either sync or async mode.

nativeHeapZeroInit enables automatic initialization of heap memory.

Both attributes default to off and can be specified at either
application or process level.

Bug: 135772972
Bug: 177438394
Bug: 178038272
Test: CtsTaggingHostTestCases

Change-Id: I6a481a9d2363997bf954f248d08224c79f0c2afb