This commit fixes responses to HEAD requests so that the value of the
Content-Length is correct per the HTTP spec. Namely, the value of this
header should be equal to the Content-Length if the request were not a
HEAD request.

This commit also fixes a memory leak on HEAD requests to the main action
that arose from the bytes on a builder not being released due to them
being dropped on the floor to ensure that the response to the main
action did not have a body.

Relates #21123