Remove unused SourceLoc in many Mach data structures (#4180)

* Remove unused srcloc in MachReloc

* Remove unused srcloc in MachTrap

* Use `into_iter` on array in bench code to suppress a warning

* Remove unused srcloc in MachCallSite

crates/cranelift/src/compiler.rs

@@ -657,7 +657,6 @@ fn collect_address_maps(
 fn mach_reloc_to_reloc(reloc: &MachReloc) -> Relocation {
     let &MachReloc {
         offset,
-        srcloc: _,
         kind,
         ref name,
         addend,
@@ -679,11 +678,7 @@ fn mach_reloc_to_reloc(reloc: &MachReloc) -> Relocation {
 }
 
 fn mach_trap_to_trap(trap: &MachTrap) -> TrapInformation {
-    let &MachTrap {
-        offset,
-        srcloc: _,
-        code,
-    } = trap;
+    let &MachTrap { offset, code } = trap;
     TrapInformation {
         code_offset: offset,
         trap_code: match code {