Make the BBAddrMap struct binary-format-agnostic.

The only binary-format-related field in the BBAddrMap structure is the function address (`Addr`), which will use uint64_t in 64B format and uint32_t in 32B format. This patch changes it to use uint64_t in both formats.
This allows non-templated use of the struct, at the expense of a marginal additional size overhead for the 32-bit format. The size of the BB address map section does not change.

Differential Revision: https://reviews.llvm.org/D112679