tsan: remove TSAN_MID_APP_RANGE macro

First, the define conflicts with definition/testing of all mappings,
since it's not a global property anymore. Second, macros/ifdefs are bad.
Define kMidAppMemBeg/End to 0 to denote that there is no "mid" range instead.

Depends on D107736.

Reviewed By: melver

Differential Revision: https://reviews.llvm.org/D107737