Add experimental "no-panic" feature.

[PiotrSikora]

When enabled, any "this should never happen" errors in dispatcher and/or hostcalls will be logged, but the processing will continue as if nothing happened, instead of panicking and trapping WasmVM.

Note that any execution past the "should have panicked" point is mostly undefined, since the state of any objects might get out-of-sync with the host when errors and/or events are being ignored.