[lldb] Actually support more than 32 logging categories

In January, Greg put up a patch (D117382) to support, among other
things, more than 32 log categories. That led to a bunch of nice
cleanups, but categories remained constrained because different parts of
the code were still using uint32_t. This patch fixes the remaining
issues and makes it possible to add a 32nd log category.

Differential revision: https://reviews.llvm.org/D134245