Issue title: Deprecate `neko.Web` and `php.Web`
 Issue body: Let's deprecate them for 4.1 and move to hx3compat in 4.2
 Comments: 
 Comment 0: What is the rationale?

_(and let's no kid ourselves: code goes to hx3compat to die)_
 Comment 1: It's out-of-scope for a standard library. At least one of our, uhm, size.
 Comment 2: Out of scope and it has very inefficient API to implement for PHP.
 Comment 3: > Let's deprecate them for 4.1 and move to hx3compat in 4.2

Should it not technically go to `hx4compat`
 Comment 4: Yes, probably
 Comment 5: Deprecated.
Next step: move to hx4compat
 Comment 6: `neko.Web` should not be derpecated as there's no alternative.
{'source': 'GithubIssues', 'repo_name_with_owner': 'HaxeFoundation/haxe', 'issue_id': 566263187, 'repo_stars': 5712.0}