Consider a typed tracing

In a similar way that we have diagnostics on `$lib` having the ability to expose ahead of time what are all the tracing options for the compiler/a library would be nice to generate/keep doc up to date.
```ts
createTypeSpecLIbrary({
name: "@typespec/http",
tracing: [
"http.validate",
"http.decorators.use",
// ...
]
})
```

or more verbose with a description
```ts
createTypeSpecLibrary({
name: "@typespec/http",
tracing: {
"http.validate": "Running http validation",
"http.decorators.use": "Using an http decorator"
// ...
}
})
```

and then we can use `getTracer(program)` which returns a typed helper that can `.trace`