fix: use registry.npmjs.com to fix shinkwrap resolves (#16607)

npm treats registry.npmjs.org as a special value that means 'the current configured package' in package-lock and npm-shrinkwrap. npm will request aws-cdk's dependencies from yarnpkg instead of from the installers configured registry because aws-cdk's shrinkwrap uses yarnpkg. This behavior seems new to [npm v7]. It causes issues for us because we run our builds with a isolated network and a private registry.

[npm v7]: npm/cli#3783

This commit changes the registry from yarnpkg to npmjs. I updated yarn.lock with sed.

```
sed 's|https://registry.yarnpkg.com|https://registry.npmjs.org|' yarn.lock -i
```
Alternatively we could modify the yarn-cling tool to replace the registry. [registry.yarnpkg.com is a cname for registry.npmjs.org](https://yarnpkg.com/getting-started/qa#why-registryyarnpkgcom-does-facebook-track-us) so changing to registry.npmjs.org shouldn't affect available packages or performance.

```
dig registry.yarnpkg.com | rg CNAME
registry.yarnpkg.com.	300	IN	CNAME	yarn.npmjs.org
```

----

*By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license*

.yarnrc

@@ -1 +1,9 @@
 --install.check-files     true      # install will verify file tree of packages for consistency
+
+# Use the npm registry instead of yarns mirror.
+# npm treats registry.npmjs.org as a special value that means 'the current
+# configured package' in package-lock and npm-shrinkwrap.  if we use
+# registry.yarnpkg.com in our shrinkwrap then users with a custom registry will
+# be forced to registry.yarnpkg.com.
+# https://github.com/npm/cli/issues/3783
+registry "https://registry.npmjs.org"