Profiler: Fix disassembling objects with a non-zero .text vaddr

Previously, we assumed that the `.text` segment was loaded at vaddr 0 in
shared object, which is not the case with `-z separate-code` enabled.
Because we didn't do the right calculations to translate an address from
a performance event into its value within the ELF file, Profiler would
try to disassemble out-of-bounds memory locations, leading to a crash.

This commit also changes `LibraryMetadata` to apply to a loaded library
as a whole, not just to one of its segments (like .text or .data). This
lets us simplify the interface, as we no longer have to worry about
`text_base`.

Fixes #10628

Userland/DevTools/Profiler/Process.h

@@ -28,7 +28,6 @@ public:
         FlatPtr base;
         size_t size;
         String name;
-        FlatPtr text_base;
         MappedObject* object { nullptr };
 
         String symbolicate(FlatPtr, u32* offset) const;