feat: add metrics host functions

[tqwewe]

This PR implements guest functionality for metrics including tracing, counters, and histograms. It is dependent on https://github.com/lunatic-solutions/lunatic/pull/202.

• [x] Add documentation for macros in metrics module.

Macros are added for logging, including span!, info!, warn!, error!, trace!. These macros are modified directly from the rust tracing crate, and the syntax is essentially identical.

Additionally, there are new types for creating metrics including:

• Meter
• Counter
• Histogram

The best place to see usage of all of it is in examples/metrics.rs.

Running lunatic with --jaeger <url> will attempt to push tracing to a jaeger endpoint. Running lunatic with --prometheus <url> will make the runtime serve metrics available at http://localhost:9927/metrics