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_ast_passes/src/ast_validation.rs

@@ -796,7 +796,7 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
 
     fn visit_expr(&mut self, expr: &'a Expr) {
         match &expr.kind {
-            ExprKind::LlvmInlineAsm(..) if !self.session.target.target.options.allow_asm => {
+            ExprKind::LlvmInlineAsm(..) if !self.session.target.options.allow_asm => {
                 struct_span_err!(
                     self.session,
                     expr.span,