fix(ngInput): change URL_REGEXP to better match RFC3987

The URL_REGEXP in use to perform validation in ngInput is too restrictive and fails to
follow RFC3987. In particular, it only accepts ftp, http, and https scheme components and
rejects perfectly valid schemes such as "file", "mailto", "chrome-extension",
etc. The regex also requires the scheme to be followed by two "/" but the RFC says
0 to n are acceptable. This change fixes both of these issues to better align to
the standard.

Closes #11341
Closes #11381