Update the documentation for Caller::get_export. (#5556)

Update the documentation for `Caller::get_export` to clarify that it's
not expected to be removed in the future. Components do offer an
alternative to `Caller::get_export`, so add a brief note mentioning
that.

Also, as of #4431 `get_export` now works for all exports, not just
memories and functions.

crates/wasmtime/src/func.rs

@@ -1726,24 +1726,23 @@ impl<T> Caller<'_, T> {
 
     /// Looks up an export from the caller's module by the `name` given.
     ///
-    /// Note that when accessing and calling exported functions, one should
-    /// adhere to the guidelines of the interface types proposal.  This method
-    /// is a temporary mechanism for accessing the caller's information until
-    /// interface types has been fully standardized and implemented. The
-    /// interface types proposal will obsolete this type and this will be
-    /// removed in the future at some point after interface types is
-    /// implemented. If you're relying on this method type it's recommended to
-    /// become familiar with interface types to ensure that your use case is
-    /// covered by the proposal.
+    /// This is a low-level function that's typically used to implement passing
+    /// of pointers or indices between core Wasm instances, where the callee
+    /// needs to consult the caller's exports to perform memory management and
+    /// resolve the references.
+    ///
+    /// For comparison, in components, the component model handles translating
+    /// arguments from one component instance to another and managing memory, so
+    /// that callees don't need to be aware of their callers, which promotes
+    /// virtualizability of APIs.
     ///
     /// # Return
     ///
-    /// If a memory or function export with the `name` provided was found, then it is
-    /// returned as a `Memory`. There are a number of situations, however, where
-    /// the memory or function may not be available:
+    /// If an export with the `name` provided was found, then it is returned as an
+    /// `Extern`. There are a number of situations, however, where the export may not
+    /// be available:
     ///
     /// * The caller instance may not have an export named `name`
-    /// * The export named `name` may not be an exported memory
     /// * There may not be a caller available, for example if `Func` was called
     ///   directly from host code.
     ///