[GlobalISel] When a tail call is emitted in a block, stop translating it

This fixes a crash in tail call translation caused by assume and lifetime_end
intrinsics.

It's possible to have instructions other than a return after a tail call which
will still have `Analysis::isInTailCallPosition` return true. (Namely,
lifetime_end and assume intrinsics.)

If we emit a tail call, we should stop translating instructions in the block.
Otherwise, we can end up emitting an extra return, or dead instructions in
general. This makes the verifier unhappy, and is generally unfortunate for
codegen.

This also removes the code from AArch64CallLowering that checks if we have a
tail call when lowering a return. This is covered by the new code now.

Also update call-translator-tail-call.ll to show that we now properly tail call
in the presence of lifetime_end and assume.

Differential Revision: https://reviews.llvm.org/D67415

llvm-svn: 371572