Bug 5106: Broken cache manager URL parsing (#788)

Bug 5106: Broken cache manager URL parsing (#788)

Use already parsed request-target URL in cache manager and
update CacheManager to Tokanizer based URL parse

Removing use of sscan() and regex string processing which have
proven to be problematic on many levels. Most particularly with
regards to tolerance of normally harmless garbage syntax in URLs
received.

Support for generic URI schemes is added possibly resolving some
issues reported with ftp:// URL and manager access via ftp_port
sockets.

Truly generic support for /squid-internal-mgr/ path prefix is
added, fixing some user confusion about its use on cache_object:
scheme URLs.

TODO: support for single-name parameters and URL #fragments
are left to future updates. As is refactoring the QueryParams
data storage to avoid SBuf data copying.