PR #39939 added support for the `Link` header being generated
automatically when using `stylesheet_link_tag` and
`javascript_include_tag`. However not everything should be
preloaded, e.g. a link to a legacy IE stylesheet has no need to be
preloaded because IE doesn't support the header and in some browsers it
will trigger the preload even though it's not used since it's inside an
IE conditional comment. This leads to increased bandwith costs and
slower application performance.

To allow more flexibility for sites that may have complex needs for the
`Link` header this commit adds a configuration option that disables it
completely and leaves it up to the application to decide how to handle
generating a `Link` header.

(cherry picked from commit 200083c2)