Add redirect.xml map for manual pages on php.net

[jordikroon]

The goal for this PR is to migrate all doc related redirects out of web-php.
Instead we generate a redirects.json from redirects.xml which is then loaded in-place.

Redirects not related to docs are NOT migrated. However shortcuts are.

Depends on:

php/phd#260

[derickr]

Right now, not all of these do a 301 redirect, but instead serve the content directly with the "legacy" URL. I think for many, that is the right goal. (As example https://www.php.net/class.oci-lob)

For others, such as https://www.php.net/@, there is a 301.

[alfsb]

The question in another PR, about the phd/Redirects class only doing validations, is in the context that I would not oppose having a .json file in doc-en, already in the final format that web-php/error.php uses. Something like:

[{"comment": "See web-php/error.php for details."}

,{"comment": "   OCI-Collection class renamed   "}
,{"redirect":"manual", "from":"class.oci-lob", "to":"class.ocilob"}
,{"redirect":"manual", "from":"oci-lob.append", "to":"ocilob.append"}

]