Mark type test intrinsics as speculatable to fix inline cost

Mark type test intrinsics as speculatable to fix inline cost

There is already code in InlineCost.cpp to identify and ignore ephemeral
values (llvm.assume intrinsics and other side-effect free instructions
only feeding the assumes). However, because llvm.type.test intrinsics
were not marked speculatable, they and any instructions specifically
feeding the type test (typically a bitcast) were being counted towards
the instruction cost when inlining. This was causing profile matching
issues in some cases when enabling -fwhole-program-vtables for whole
program devirtualization.

According to the language reference, the speculatable attribute means:
"the function does not have any effects besides calculating its result
and does not have undefined behavior". I see no reason why type tests
cannot be marked with this attribute.

There are 2 test changes:

llvm/test/Transforms/Inline/ephemeral.ll: I added a type test intrinsic
here to verify the fix. Also, I found the test was not actually testing
what it originally intended. Many of the existing instructions were
optimized away by -Oz, and the cost of inlining was negative due to the
benefit of removing the call. So I changed the test to simply invoke the
inline pass and check the number of instructions computed by InlineCost.
I also fixed an instruction that was not actually used anywhere.

llvm/test/Transforms/SimplifyCFG/no-md-sink.ll needed to be made more
robust to code changes that reordered the metadata.

Differential Revision: https://reviews.llvm.org/D101180