VS: Revert "Add support for ASAN -fsanitize=address flag"

Revert commit 1b37305b (VS: Add support for ASAN -fsanitize=address
flag, 2021-04-21).  The tag `EnableASAN` is created in
`ItemDefinitionGroup` but it needs to be in `PropertyGroup`.  Revert the
mapping pending an implementation in the generator.

Issue: #21081