Support pre-flight CORS check (#1772)

## Issue Addressed

- Resolves #1766 

## Proposed Changes

- Use the `warp::filters::cors` filter instead of our work-around.

## Additional Info

It's not trivial to enable/disable `cors` using `warp`, since using `routes.with(cors)` changes the type of `routes`.  This makes it difficult to apply/not apply cors at runtime. My solution has been to *always* use the `warp::filters::cors` wrapper but when cors should be disabled, just pass the HTTP server listen address as the only permissible origin.

common/warp_utils/src/lib.rs

@@ -1,6 +1,6 @@
 //! This crate contains functions that are common across multiple `warp` HTTP servers in the
 //! Lighthouse project. E.g., the `http_api` and `http_metrics` crates.
 
+pub mod cors;
 pub mod reject;
-pub mod reply;
 pub mod task;