WASM Exceptions And Tag Import/Export

[martindevans]

• Added support for WASM tag types (import/export)
• Added support for enabling WASM exceptions

This adds the ability to load modules which depend upon WASM exceptions. It does not add any support for catching, throwing or interacting with exceptions in any way (still working on that for a follow-up PR).

[Avril112113]

I've been working on adding proper exceptions handling along with @martindevans (for a separate PR)
I've tested the tag import and exports in a project of mine, besides the tag Parameters, but the tests cover those anyway.

From prior testing, enabling exceptions in the config is no issue if there is no C# call boundary.
However, if there is a C# call boundary, a trap is triggered which boils all the way down in C# only, skipping WASM entirely.
So until the next PR, it's worth noting as it could be odd behaviour for WASM expecting to catch (for example, with setjmp/longjmp).

[jsturtevant]

Is the next pr in flight? Should we wait on this or is it ready to go?