base: Fix #25066 via `noinline`
As noted in #25066 (closed), the exception backtrace proposal introduced a rather subtle performance regression due to simplification producing Core which the demand analyser concludes may diverge with a precise exception. The nature of the problem is more completely described in the new Note [Hiding precise exception signature in throw].
The (rather hacky) solution we use here hides the problematic
optimisation through judicious use of noinline
. Ultimately however we
will want a more principled solution (e.g. #23847).