feat: expose building a CompiledPlugin with a fuel limit (#883)

Expose a new method `extism_compiled_plugin_new_with_fuel_limit` to
build a CompiledPlugin with a fuel limit.

Fixes #882

feat: expose building a CompiledPlugin with a fuel limit (#883)

Expose a new method `extism_compiled_plugin_new_with_fuel_limit` to
build a CompiledPlugin with a fuel limit.

Fixes #882

fix: use gh release download instead of downloading from github actio…

…n artifacts in dotnet workflow (#857)

It seems like at some point we changed the `release.yml` workflow to
create multiple artifacts instead of one `release-artifacts` tarball. I
changed the .NET Nuget workflow to be more like Python

fix: remove unwrap() from extism_compiled_plugin_new

`extism_compiled_plugin_new` would panic on bad manifest input (there's
a test in the python sdk [1] that hits this directly.) Catch the error and
set `errmsg` appropriately instead.

Additionally: golf the function pointer casting for the various `plugin_new` calls,
with the goal of reducing the number of allocations by leaning on iterator size
hints (and reducing the scope of `unsafe{}` use.) This part can be severed: it
introduces a breaking change. Previously `NULL` values were silently accepted in
the `functions**` list; now they fail. This maintains consistency with behavior on
"consumed" `ExtismFunction` pointer.

[1]: https://github.com/extism/python-sdk/blob/main/tests/test_extism.py#L50-L53