Introduce `AddressSpaceView` template parameter to `CombinedAllocator`.

Summary:
This is a follow up to https://reviews.llvm.org/D55764 .

For the ASan and LSan allocatorsthe type declarations have been modified
so that it's possible to create a combined allocator type that
consistently uses a different type of `AddressSpaceView`. We intend to
use this in future patches. For the other sanitizers they just use
`LocalAddressSpaceView` by default because we have no plans to use these
allocators in an out-of-process manner.

rdar://problem/45284065

Reviewers: kcc, dvyukov, vitalybuka, cryptoad, eugenis, kubamracek, george.karpenkov, yln

Subscribers: #sanitizers, llvm-commits

Differential Revision: https://reviews.llvm.org/D55766

llvm-svn: 349957