[NFC][scudo] Extract MapAllocatorTest for TEST_F am: d3199321d7 am: 1fa4b12b3d am: 2046628791 am: a7916346bf

Original change: https://android-review.googlesource.com/c/platform/external/scudo/+/1763652

Change-Id: I203c6e177220f23078ea3131f1dd5784a9cdd627