Support redirects for non-collection resources

[jwodder]

Please add support for GETing a non-collection resource when the server responds with a redirect to another URL. Currently, webdavfs does not support redirects at all; attempting to access a redirected file over a webdavfs mount results in the following in the trace file:

GET request error: Get "<REDIRECTED URL>": 400 Will not follow redirect
2024-02-27 09:32:08 GetRange: Get "<REDIRECTED URL>": 400 Will not follow redirect
2024-02-27 09:32:08 102 Read(FILENAME): Get "<REDIRECTED URL>": 400 Will not follow redirect