Keep symbol map entries from between modules

This helps for when we add modules (like sceCcc) and when a game loads and unloads modules.  I use these files not only for the debugger and renaming funcs, but also to scan for usage of sce* funcs.  But it wasn't accurate since modules loaded later would either skip updating the symbol map, or erase previous entries.

This keeps a unique std::set of the address/size/types, and then always adds.

Also made a bunch of things const because I wanted to be sure I didn't miss anything that was mutating `entries`.

-[Unknown]