[llvm-exegesis] Validate that address annotations are aligned (#75554)

This patch adds in validation at two different levels that address
annotations are page aligned. This is necessary as otherwise the mmap
calls will fail as MAP_FIXED/MAP_FIXED_NOREPLACE require page aligned
addresses. This happens silently in the subprocess. This patch adds
validation at snippet parsing time to give feedback to the user and also
adds asserts at code generation/address usage time to ensure that other
users of the Exegesis APIs conform to the same requirements.