Improve debuggability by adding original host function exceptions to TrapException

[peterhuene]

Right now if a host function throws a .NET exception, the exception is caught and translated to a trap representation.

The trap representation only keeps the exception message. When the trap bubbles back up to .NET, the trap is thrown as a TrapException.

Since only the message is kept, debugging the source of the host function exception can be difficult, especially from a log that prints only the TrapException.

When a trap representation is created, the original caught exception should be stored somewhere that can be utilized from where TrapException is thrown and passed in as the inner exception.

[alexhiggins732]

I am currently in this area of code in PR #95 and not sure what else can be done here.

We are already capturing the web assembly error message as a string and work has already been done to utilize the methods within the c bindings in trap.h to walk the stack:

Functions:

wasm_trap_t * wasmtime_trap_new (const char *msg, size_t msg_len)
Creates a new trap. More...

bool wasmtime_trap_code (const wasm_trap_t *, wasmtime_trap_code_t *code)
Attempts to extract the trap code from this trap. More...

bool wasmtime_trap_exit_status (const wasm_trap_t *, int *status)
Attempts to extract a WASI-specific exit status from this trap. More...

const wasm_name_t * wasmtime_frame_func_name (const wasm_frame_t *)
Returns a human-readable name for this frame's function. More...

const wasm_name_t * wasmtime_frame_module_name (const wasm_frame_t *)
Returns a human-readable name for this frame's module. More...

Please let me know if there was something else you had in mind.