std: Restore conventional compareFn behavior for binarySearch

PR #20927 made some improvements to the `binarySearch` API, but one
change I found surprising was the relationship between the left-hand and
right-hand parameters of `compareFn` was inverted. This is different
from how comparison functions typically behave, both in other parts of
Zig (e.g. `std.math.order`) and in other languages (e.g. C's `bsearch`).
Unless a strong reason can be identified and documented for doing
otherwise, I think it'll be better to stick with convention.

While writing this patch and changing things back to the way they were,
the predicates of `lowerBound` and `upperBound` seemed to be the only
areas that benefited from the inversion. I don't think that benefit is
worth the cost, personally. Calling `Order.invert()` in the predicates
accomplishes the same goal.

lib/std/debug/SelfInfo.zig

@@ -1624,12 +1624,12 @@ pub fn unwindFrameDwarf(
     } else {
         const index = std.sort.binarySearch(Dwarf.FrameDescriptionEntry, di.fde_list.items, context.pc, struct {
             pub fn compareFn(pc: usize, item: Dwarf.FrameDescriptionEntry) std.math.Order {
-                if (pc < item.pc_begin) return .gt;
+                if (pc < item.pc_begin) return .lt;
 
                 const range_end = item.pc_begin + item.pc_range;
                 if (pc < range_end) return .eq;
 
-                return .lt;
+                return .gt;
             }
         }.compareFn);