`Fetcher::getByUri()` returns a string (and since it is a public method
we don't want to change that for now), but we check for `false`; so we
change that.

We also use `file_exists()` instead of `Cache::isFileCached()` because
the method is actually called `Cache::fileIsCached()` but appears to be
broken due to applying `::getCacheablePath()` again.  Furthermore the
other methods of `Cache` also use `file_exists()` directly.  Since
`Cache::fileIsCached()` is public, we do not remove the otherwise
unused method yet.

We set executable permissions for all .bat and .exe files.  This is
required for running in Cygwin shells, but generally considered good
style.

* Declare methods and instance variables in abstract classes

While PHP doesn't require this, it is good style, and makes the code
easier to reason about.

* Declare class variable

While `Config::getSdkNugetFeedUrl()` is not used from within the
project, and probably just was some experimental stuff, the method is
public, so we better keep it for now, but avoid reading an undeclared
class variable.

* Dodge from covariance warnings regarding Iterator for now

* Don't pass unnecessary arguments

These are retrieved from within the called functions, what *might* not
be the best idea, but it's what we have for now.

* Assert that $cb is actually a string before string conversion

In practice, it's either "copy" or "rename".

* Declare missing `Server::getPhp()`

* Remove unreachable code

* Ensure that `$crt` is defined

From looking at the code, it seems so, but let's make sure before
reading an undefined variable.

* Config::getDepsPort() returns an int

While that is changing the signature of a public method, it makes no
sense to return a string, and later to convert to int again.

* The abstract class TrainingCase is an Interfaces\TrainingCase

There shouldn't be the need for even having an interface (an abstract
class should be sufficient), but we keep the interface for now.

Some are not as specific as they should be, and some may even be wrong,
but since these are only type hints (not type declarations) they won't
affect code execution, but rather provide some help to better understand
the code – for developers as well as tooling.

The composer version requirement has long been fixed[1], so we can drop
the respective comment also.

[1] <php@8583bb4>

As of PHP 8.2.0, ext/zip is no longer statically available, but since
it is needed by the PHP SDK (e.g. too unpack the fetched dependencies),
we include the DLL, and load it in php.ini.

ext/zip is no longer statically compiled as of PHP 8.2.0, but is needed
for several setup tasks; thus we load the shared extension.

That is the latest stable version, and certainly progress over Nginx
1.17.6 which has been released almost five years ago.

The file `VERSION` used to send the version contains a new line.

When it's used to generate the UserAgent for curl, the new line char
stops the headers sent for the request. All other headers sent after the
user agent are ignored and used like the body requests.

To solve this issue, clean up the `VERSION` file content on load.

- Replace deprecated WMIC command with modern PowerShell
- Use Get-CimInstance instead of WMIC to access Win32_Processor
- Maintain compatibility with existing code by keeping same output format
- Improve compatibility with newer Windows versions
- No changes to core program logic

We also update to 2.4.0-dev.

Closes php#41.

Closes phpGH-42.