Unwieldy Target subclasses signature improvements

[douglas-raillard-arm]

Target subclasses have grown somewhat unwieldy over the years in 2 ways:

• Some parameters logically related are spread apart in the signature due to the order in which they were introduced in the code.
• A lot of these parameters are shoveled around to super().__init__(), making adding new parameters more error prone than it should be and duplicating default values for those everywhere.

To address that, moving most arguments to being keyword-only would ensure:

1. the user code stays sane
2. Target subclasses could mostly be forwarding **kwargs to the super class where possible.
3. We would not duplicate default values everywhere anymore

The main cons are:

1. It's an API breaking change. However:
   • I would suspect the vast majority of user code either does not set those parameters or already uses keyword arguments syntax
   • Once the user code is fixed, the user code is backward and forward compatible so they can still switch to older devlib versions if needed.
   • This can be done after a grace period where we emit a DeprecationWarning when any positional argument is used.
2. Depending on how the documentation is dealt with, this can affect the visible signature. However:
   • The current style of doc is completely separate from the code and would not be affected.
   • The equivalent docstring style would not really be affected, and decorators can be implemented to make the signature look better (I did in LISA and it works fine).
   • There is a reasonable chance that type annotation these days can help recover decent autocompletion on a **kwargs signature, but I'd need to check the details.