[WebAssembly] Error out on indirect uses of setjmp

Both Wasm & Emscripten SjLj handling has a restriction that `setjmp`
cannot be called indirectly. I thought we have been erroring out on
indirect uses of `setjmp`, but some recent CL disrupted the logic and
we are not erroring out anymore.

We currently
1. Collect functions that contain `setjmp` calls in `SetjmpUsers`. This
   only counts direct calls:
   https://github.com/llvm/llvm-project/blob/8f77dc459e31aad6daab89a124fa92067916274c/llvm/lib/Target/WebAssembly/WebAssemblyLowerEmscriptenEHSjLj.cpp#L869-L878
2. Run `runSjLjOnFunction` only on those `SetjmpUsers`. Within
   `runSjLjOnFunction`, if we see an indirect use of `setjmp`, we error
   out:
   https://github.com/llvm/llvm-project/blob/8f77dc459e31aad6daab89a124fa92067916274c/llvm/lib/Target/WebAssembly/WebAssemblyLowerEmscriptenEHSjLj.cpp#L1218-L1221

So if there are only indirect setjmp calls within the module,
`SetjmpUsers` will be empty, and `runSjLjOnFunction` is not even entered
once. And the indirect `setjmp` call will error out at link time. So in
this CL we check for the indirect uses of `setjmp` upfront before we
enter `runSjLjOnFunction`.

Also this currently errors out on `invoke @setjmp`, which can only occur
when using Wasm EH + Wasm SjLj within a function. We recently added Wasm
SjLj support but we don't support using Wasm EH + Wasm SjLj in the same
function yet. We plan to add this support very soon, so I don't think
it's worth creating another test file just for this. (This is an error
test so it needs its own file)

Reviewed By: dschuff

Differential Revision: https://reviews.llvm.org/D109375