text: Title: Positional-only argument containing `=` is considered named argument if keyword accepts `**named`
  Body: If a keyword accepts a positional only argument like
  ```python
  def example(arg, /):
      print(arg)
  ```
  using it like
  ```
  Example    foo=bar
  Example    arg=xxx
  ```
  works fine and the keyword gets `foo=bar` and `arg=xxx` as an argument, respectively. The argument is positional-only so `=` has no special meaning.
  
  If the keyword also accepts free named arguments like
  ```python
  def example(arg, /, **named):
      print(arg, named)
  ```
  using it like
  ```
  Example    foo=bar
  ```
  fails like 
  > Keyword 'example.Example' expected 1 non-named argument, got 0.
  
  This is due to a bug in argument resolving logic where all arguments containing `=` are considered named if the keyword accepts free named arguments. This needs to be fixed so that positional-only arguments are excluded.
  
  After the fix we can fix #4821 by changing the signature of the `Format String` keyword to `template, /, *positional, **named`. We also should check are there other keywords accepting `**named` that could get the same treatment.