[scudo] Tuning changes based on feedback from current use

Summary:
This tunes several of the default parameters used within the allocator:
- disable the deallocation type mismatch on Android by default; this
  was causing too many issues with third party libraries;
- change the default `SizeClassMap` to `Dense`, it caches less entries
  and is way more memory efficient overall;
- relax the timing of the RSS checks, 10 times per second was too much,
  lower it to 4 times (every 250ms), and update the test so that it
  passes with the new default.

Reviewers: eugenis

Reviewed By: eugenis

Subscribers: srhines, delcypher, #sanitizers, llvm-commits

Differential Revision: https://reviews.llvm.org/D57116

llvm-svn: 352057