Replace target.target with target and target.ptr_width with target.pointer_width

Preparation for a subsequent change that replaces
rustc_target::config::Config with its wrapped Target.

On its own, this commit breaks the build. I don't like making
build-breaking commits, but in this instance I believe that it
makes review easier, as the "real" changes of this PR can be
seen much more easily.

Result of running:

find compiler/ -type f -exec sed -i -e 's/target\.target\([)\.,; ]\)/target\1/g' {} \;
find compiler/ -type f -exec sed -i -e 's/target\.target$/target/g' {} \;
find compiler/ -type f -exec sed -i -e 's/target.ptr_width/target.pointer_width/g' {} \;
./x.py fmt

compiler/rustc_target/src/spec/mod.rs

@@ -1619,10 +1619,7 @@ impl ToJson for Target {
 
         target_val!(llvm_target);
         target_val!(target_endian);
-        d.insert(
-            "target-pointer-width".to_string(),
-            self.pointer_width.to_string().to_json(),
-        );
+        d.insert("target-pointer-width".to_string(), self.pointer_width.to_string().to_json());
         target_val!(target_c_int_width);
         target_val!(arch);
         target_val!(target_os, "os");