Add a CodeBuilder type to the wasmtime crate

[alexcrichton]

This commit is extracted from #8055 and adds a new CodeBuilder type which is intended to be able to further configure compilation beyond what the constructors of Module already provide. For example in #8055 knobs will be added to process *.dwp files for more debuginfo processing.

[alexcrichton]

I'll note that while I've called this ModuleBuilder it actually supports components as well, so there's probably a better name for this.

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[fitzgen]

LGTM!

As far as naming goes, the only alternatives I can think of are

• ModuleOrComponentBuilder
• CodeBuilder

Or maybe splitting this type in two in the public API (and sharing an underlying impl) so that we have both a ModuleBuilder and a ComponentBuilder.

[fitzgen]

Suggested change

	/// WebAssembly module. Less advanced configuration can use constructors such
	/// as:
	/// WebAssembly module. Most configuration can use simple constructors such
	/// as:

[fitzgen]

(Don't want to create a weird "advanced" vs not thing where people who consider themselves Serious Wasmtime Users will want to use this without actually having a good reason. Might be overthinking things here.)

[alexcrichton]

It feels kind of nice being able to configure components/modules in one builder since it's all wasm anyway so I think I'll stick with one for now vs copying APIs, but I'll rename to CodeBuilder as I like that name more.