fix consistency in parameter names + some cleanup

[azjezz]

No description provided.

[veewee]

Looks OK!
How are we going to keep this consistent without having to create a cleanup PR every once in a while?

[azjezz]

not sure how we can enforce this later in CI.

there's a lot of rules we have that are currently not enforced by CI:

• a file can only contain 1 function declaration
• Psl\Foo\Bar\Baz\qux function must be declared in src/Psl/Foo/Bar/Baz/qux.php
• function name must be in snake_case
• argument name must be in snake_case
• constant Psl\Foo\Bar\BAZ_QUX must be declared in src/Psl/Foo/Bar/constants.php
• all classes should be declared either final or abstract ( unless its an exception )
• interface names should end with Interface suffix
• abstract classes should have the Abstract prefix
• traits should end with Trait suffix
• closure should always be declared static, even within functions, when $this is not used.
  .... and more

[veewee]

Added the list to #30
I think there are at least some of them that we can tackle with cs