Trap when trying to raise wasm32 exceptions

[lbguilherme]

We don't support WASM exceptions yet. But in the mean time, let's at least get an usable stack trace there! It's a small quality of life improvement.

Before:

$ wasmtime run benchmark_spec 
EXITING: Attempting to raise:
Not Implemented: Crystal::EventLoop.create_resume_event (NotImplementedError)

After:

$ wasmtime run benchmark_spec 
EXITING: Attempting to raise:
Not Implemented: Crystal::EventLoop.create_resume_event (NotImplementedError)
Error: failed to run main module `benchmark_spec`

Caused by:
    0: failed to invoke command default
    1: wasm trap: wasm `unreachable` instruction executed
       wasm backtrace:
           0: 0x18c68 - <unknown>!*raise<NotImplementedError>:NoReturn
           1: 0xfcf06 - <unknown>!*Crystal::EventLoop::create_resume_event<Fiber>:NoReturn
           2: 0x7ae95 - <unknown>!*Fiber#resume_event:Crystal::Event
           3: 0xfe2aa - <unknown>!*Crystal::Scheduler#sleep<Time::Span>:Nil
           4: 0xfe259 - <unknown>!*Crystal::Scheduler::sleep<Time::Span>:Nil
           5: 0x1a776 - <unknown>!*sleep<Float64>:Nil
           6: 0x1a654 - <unknown>!~procProc(Nil)@spec/std/benchmark_spec.cr:16
           7: 0x159bc7 - <unknown>!*Benchmark::IPS::Entry#call:Nil
           8: 0x156d0c - <unknown>!*Benchmark::IPS::Job#run_warmup:Nil
           9: 0x156a77 - <unknown>!*Benchmark::IPS::Job#execute:Nil
          10: 0x1a3bc - <unknown>!~procProc(Nil)@spec/std/benchmark_spec.cr:12
          11: 0x123110 - <unknown>!*Spec::Example#internal_run<Time::Span, Proc(Nil)>:(Array(Spec::Result) | Nil)
          12: 0x122f49 - <unknown>!*Spec::Example#run:Nil
          13: 0x121a67 - <unknown>!*Spec::ExampleGroup@Spec::Context#internal_run:Nil
          14: 0x12170d - <unknown>!*Spec::ExampleGroup#run:Nil
          15: 0x10fe69 - <unknown>!*Spec::RootContext@Spec::Context#internal_run:Nil
          16: 0x10fd44 - <unknown>!*Spec::RootContext#run:Nil
          17: 0x18f0d - <unknown>!~procProc(Int32, (Exception | Nil), Nil)@src/spec/dsl.cr:216
          18: 0xfe7cb - <unknown>!*Crystal::AtExitHandlers::run<Int32, (Exception+ | Nil)>:Int32
          19: 0x1690fb - <unknown>!*Crystal::exit<Int32, (Exception+ | Nil)>:Int32
          20: 0x16909c - <unknown>!*Crystal::main<Int32, Pointer(Pointer(UInt8))>:Int32
          21: 0x17ca9 - <unknown>!main
          22: 0x17d2b - <unknown>!main
          23: 0x16c6ef - <unknown>!__main_void
          24: 0x17cda - <unknown>!_start
       note: using the `WASMTIME_BACKTRACE_DETAILS=1` environment variable to may show more debugging information

Note that it is not possible to catch or recover from this trap.