[QA] more errors with extra slashes in URI

Seen while testing https://github.com/owncloud/core/issues/34365 with 10.11.0-beta.1

The following cases are fixed since #40216:

• curl -u admin:admin http://localhost//remote.php//dav/files/admin/test.txt # double slashes at start
• curl -u admin:admin http://localhost//remote.php//dav//files//admin//test.txt # double slashes everywhere
• curl -u admin:admin http://localhost////remote.php//dav/files/admin/test.txt # many slashes at start

This still explodes

• curl -u admin:admin http://localhost/remote.php///dav/files/admin/test.txt # many slashes after remote.php

< HTTP/1.1 500 Internal Server Error
< Date: Tue, 06 Sep 2022 07:17:11 GMT
< Server: Apache/2.4.41 (Ubuntu)
...
< Content-Length: 270
< Connection: close
< Content-Type: application/xml; charset=utf-8
< 
<?xml version="1.0" encoding="utf-8"?>
<d:error xmlns:d="DAV:" xmlns:s="http://sabredav.org/ns">
  <s:exception>LogicException</s:exception>
  <s:message>Requested uri (/remote.php///dav/files/admin/test.txt) is out of base uri (/remote.php/dav/)</s:message>
</d:error>

Expected behaviour:

• redundant slashes are harmless.

Start by reproducing the failing curl request against /remote.php///dav/files/admin/test.txt and compare it with the cases fixed by #40216. Trace how the remote.php and DAV base URIs are parsed, then verify that redundant slashes after remote.php no longer produce a 500 response and that the existing cases remain working.