[lldb] Increase the default timeouts when running under ASan

Increase the default timeouts when running under ASan. We had something
similar before we adopted tablegen, but the larger timeouts got lost in
the transition, possibly because tablegen's preprocessor support is very
limited. This patch passes a new define (LLDB_SANITIZED) to
lldb-tablegen on which we can base the default value.

Differential revision: https://reviews.llvm.org/D156279