[sanitizer] Minor 32-bit primary improvements

Summary:
For the 32-bit TransferBatch:
- `SetFromArray` callers have bounds `count`, so relax the `CHECK` to `DCHECK`;
- same for `Add`;
- mark `CopyToArray` as `const`;
For the 32-bit Primary:
- `{Dea,A}llocateBatch` are only called from places that check `class_id`,
  relax the `CHECK` to `DCHECK`;
- same for `AllocateRegion`;
- remove `GetRegionBeginBySizeClass` that is not used;
- use a local variable for the random shuffle state, so that the compiler can
  use a register instead of reading and writing to the `SizeClassInfo` at every
  iteration;
For the 32-bit local cache:
- pass the count to drain instead of doing a `Min` everytime which is at times
  superfluous.

Reviewers: alekseyshl

Reviewed By: alekseyshl

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

Differential Revision: https://reviews.llvm.org/D46657

llvm-svn: 332478