AddressSanitizer support

[wenyuzhao]

We should put ASan checks as part of the CI, or at least provide basic guidance and support to use asan for debugging.

Bugs like #750 can be easily identified by asan.

[qinsoon]

We need to use an address range that is allowed by ASAN for our heap. See #1088 (comment).

ASAN divides the address space into a few ranges. It reserves some ranges as shadow memory (metadata) so it can map other address ranges to a byte in the shadow memory. On x86_64, the following is what ASAN uses (ASAN_OPTIONS=verbosity=1 prints this). Basically we are allowed to use address ranges in HighMem and LowMem, but not the range in shadow memory. ShadowGap is by default protected (and are not allowed to use), but can be unprotected by ASAN_OPTIONS=protect_shadow_gap=false.

|| [0x10007fff8000, 0x7fffffffffff] || HighMem ||
|| [0x02008fff7000, 0x10007fff7fff] || HighShadow ||
|| [0x00008fff7000, 0x02008fff6fff] || ShadowGap ||
|| [0x00007fff8000, 0x00008fff6fff] || LowShadow ||
|| [0x000000000000, 0x00007fff7fff] || LowMem ||

MMTk currently uses 0x020000000000 to 0x220000000000, which clashes with HighShadow. Also the address range we use for side metadata starts from 0x0c0000000000, also clashes with HighShadow (it also clashes with the 6th space. See #458).