[Sanitizer][RISCV][AArch64][Android] Adjust allocator tests

On 64-bit systems with small VMAs (e.g. 39-bit) we can't use
`SizeClassAllocator64` parameterized with size class maps containing a
large number of classes, as that will make the allocator region size too
small (< 2^32). Several tests were already disabled for Android because
of this.

This patch provides the correct allocator configuration for RISC-V
(riscv64), generalizes the gating condition for tests that can't be
enabled for small VMA systems, and tweaks the tests that can be made
compatible with those systems to enable them.

Differential Revision: https://reviews.llvm.org/D97234