Here we increase the similarity between the A64 and A32 front-ends in terms of their
page_table handling code. In this commit, we:
* Reserve and use r14 as a register to store the page_table pointer.
* Align the code to be more similar in structure.
* Add a conf member to A32EmitContext.
* Remove scratch argument from EmitVAddrLookup.
Several issues:
1. Several terminal instructions did not stop at the end of a single-step block
2. x64 backend for the A32 frontend sometimes polluted upper_location_descriptor with the single-stepping flag
We also introduce the enable_optimizations parameter to the A32 frontend.
Most of the time when this occurs, it's a bug. Thankfully this isn't the
case. However, we can resolve these cases to make the codebase more
consistent.
