sea: support sea.getRawAsset()

This patch adds support for `sea.getRawAsset()` which is
similar to `sea.getAsset()` but returns the raw asset
in an array buffer without copying. Users should avoid
writing to the returned array buffer. If the injected
section is not marked as writable or not aligned,
writing to the raw asset is likely to result in a crash.

PR-URL: https://github.com/nodejs/node/pull/50960
Refs: https://github.com/nodejs/single-executable/issues/68
Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com>
Reviewed-By: Stephen Belanger <admin@stephenbelanger.com>

lib/sea.js

@@ -71,5 +71,6 @@ function getAssetAsBlob(key, options) {
 module.exports = {
   isSea,
   getAsset,
+  getRawAsset,
   getAssetAsBlob,
 };