Stop testing some soon-to-be impossible cases

BoringSSL is no longer letting you half-initialize a key by setting the
type while leaving the data NULL, as this was never a coherent state.
Stop testing this in CrOS, as this is blocking the BoringSSL roll.

In reality, almost all of these error conditions are impossible, as they
can only be reached if you contort BoringSSL into constructing invalid
objects for you, by using APIs that shouldn't exist. But as these error
conditions nominally exist, I've replaced the RSA one with a different
such error condition that is, for now, still reachable.

In the long run, however, they should be removed. Every one of these is
actually just an API bug we should fix. kcer code would ideally have
been architected so that it can guarantee in the type system that these
cases are impossible, and then just CHECK-fail the unreachable cases.

Change-Id: Id05309993b7ed00bc211bb29dff3b120c157764b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6875984
Reviewed-by: Michael Ershov <miersh@google.com>
Commit-Queue: Michael Ershov <miersh@google.com>
Auto-Submit: David Benjamin <davidben@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1505746}