Port create_php_tags to Python3 and generate new PHP tags file

[eht16]

Related to #2615.

I don't know how good the newly generated tags are, my PHP knowledge is basically non-existent anymore :). At least, the diff looks like some were added, removed and changed, some keep even unchanged.

[eht16]

When #3039 is merged, I would adjust the script to generate ctags file format and share the code with the Python tags script.

[cwendling]

I don't know much PHP anymore either, but at least the script seems to still work, the difference seem to be in the JSON itself (I only checked a couple things, but they match).
Sadly the JSON seems to have a few flaws with the types in signatures (no alternative types, and it seems to use the last one which sometimes is null -- that used to be mixed in the PHP docs, but now is foo|bar|baz), but then again nothing the script can do with that data so I'd think it's fine.

[elextr]

Is there a reason that Python tags are in ctags format and php tags in tagmanager?

[eht16]

Is there a reason that Python tags are in ctags format and php tags in tagmanager?

Before #3039, Python tags were also in tagmanager format and so are the PHP tags.

As said in #3488 (comment), I would switch the format to ctags for the PHP tags as well. But I'd like to make this iterative to avoid a huge "I do it all in one"-PR :).