Consolidate Oak ABI documentation

[tiziano88]

Currently the documentation of ABI-level functions is partially replicated in various places. In some cases it makes sense for it to be more precise in the context of a particular object or programming language, but I wonder whether we can do a better job at least at cross-referencing these various pieces together.

For instance, for the node_create call:

Runtime object:

oak/oak/server/rust/oak_runtime/src/runtime/mod.rs

Lines 787 to 798 in bc98624

	/// Thread safe method that attempts to create a Node within the [`Runtime`] corresponding to a
	/// given module name and entrypoint. The `reader: ChannelReader` is passed to the newly
	/// created Node.
	///
	/// The caller also specifies a [`Label`], which is assigned to the newly created Node. See
	/// <https://github.com/project-oak/oak/blob/master/docs/concepts.md#labels> for more
	/// information on labels.
	///
	/// This method is defined on [`Arc`] and not [`Runtime`] itself, so that
	/// the [`Arc`] can clone itself and be included in a [`RuntimeProxy`] object
	/// to be given to a new Node.
	pub fn node_create(

oak_abi crate:

oak/oak/server/rust/oak_abi/src/lib.rs

Lines 131 to 142 in bc98624

	/// Create a new Node instance running code identified by configuration
	/// name and entrypoint; the entrypoint is only used when creating a
	/// WebAssembly Node; it is ignored when creating a pseudo-Node.
	///
	/// The configuration name is provided in the memory area given by
	/// `config_buf` and `config_len`; the entrypoint name is provided in the
	/// memory area given by `entrypoint_buf` and `entrypoint_len`.
	///
	/// Returns the status of the operation, as an [`OakStatus`] value.
	///
	/// [`OakStatus`]: crate::OakStatus
	pub fn node_create(

Oak ABI documentation:

https://github.com/project-oak/oak/blob/bc98624bdcf6629c4f3ef4aa139bd4a0892f3744/docs/abi.md#node_create

@daviddrysdale do you have any ideas / suggestions?

[daviddrysdale]

Is this the same as #812 ?

[daviddrysdale]

Some of the duplicate comments have been removed (two copies dropped in #883, one in #979).

Current places that describe ABI functions, using node_create as an example:

• ABI doc has a description in terms of a WebAssembly host function signature.
• oak_abi::node_create has a description in terms of a Rust unsafe function.
• (wasm::WasmInterface::node_create redirects to the ABI doc.)
• (wasm::WasmInterface::invoke_index is silent.)
• (wasm::oak_resolv_func is silent.)
• (RuntimeProxy::node_create redirects to Runtime::node_create)
• Runtime::node_create has a description in terms of native/internal Rust types.

De-duped enough?