Add support for gas metering to cranelift backend

[ethanfrey]

Thanks for proposing a new feature!

Motivation

As I worked to expose gas metering in the C API, I discovered that it was not supported with the default cranelift backend. The wasmer team assured me this is a known issue and on their roadmap.

It would be nice to enable metering without having to switch backends (unless one wants to), and also make less headache in configuration. However, this is not urgent. Mainly I wanted an issue to track progress.

Proposed solution

Support for for StreamingCompiler with middleware when using wasmer_clif_backend::CraneliftModuleCodeGenerator.

This can be easily tested on the #736 branch (or master when merged) by going into runtime-c-api package and executing cargo test --features metering.

Alternatives

Officially mark that middleware is not supported with cranelift. But I think this feature is desired, just not enough devs to implement it.

Additional context

Add any other context or screenshots about the feature request here.

[syrusakbary]

Awesome. Thanks for creating the issue so we can keep track of this over time :)

[nlewycky]

@MarkMcCaskey is implementing the alternative suggestion in #817 now .

I think there's two ways to handle this:
a) We replace the cranelift-wasm crate with our own implementation. This allows us to fix this bug by permitting access to the VM internals section where we keep the counters for metering. This has other benefits, such as decoupling our cranelift and wasmparser.rs version upgrades.
b) We write a wasm-->wasm rewriter that adds metering to any wasm code keeping the result as valid, generic, wasm code. This means we couldn't use our VM internals to keep count, but it would work with all backends, including other VMs if we wrote the modified wasm out to disk.

[syrusakbary]

In the refactor, all compilers will support any kind of middleware, including metering.

Will close this issue once we merge the refactor into master.

[syrusakbary]

Closing this issue in favor of #1418