typeck: Ensure proper bound vars passed to add_bounds.

Fixes the ICE in #88586.

src/test/ui/higher-rank-trait-bounds/issue-88586-hr-self-outlives-in-trait-def.rs

@@ -0,0 +1,11 @@
+// Regression test for #88586: a higher-ranked outlives bound on Self in a trait
+// definition caused an ICE when debug_assertions were enabled.
+//
+// The error output is incidentally unhelpful; this should be improved.
+
+trait A where for<'a> Self: 'a
+//~^ ERROR the parameter type `Self` may not live long enough
+{
+}
+
+fn main() {}

src/test/ui/higher-rank-trait-bounds/issue-88586-hr-self-outlives-in-trait-def.stderr

@@ -0,0 +1,19 @@
+error[E0311]: the parameter type `Self` may not live long enough
+  --> $DIR/issue-88586-hr-self-outlives-in-trait-def.rs:6:1
+   |
+LL | / trait A where for<'a> Self: 'a
+LL | |
+LL | | {
+LL | | }
+   | |_^
+   |
+   = help: consider adding an explicit lifetime bound `Self: 'a`...
+   = note: ...so that the type `Self` will meet its required lifetime bounds...
+note: ...that is required by this bound
+  --> $DIR/issue-88586-hr-self-outlives-in-trait-def.rs:6:29
+   |
+LL | trait A where for<'a> Self: 'a
+   |                             ^^
+
+error: aborting due to previous error
+