Use consistent arguments for load_read and load_seek

[radarhere]

load_read() does not have a consistent signature across the plugins where it is used. For example, https://github.com/python-pillow/Pillow/blob/9923531742726419732618c6f2aef0bb8c21e259/src/PIL/JpegImagePlugin.py#L411 https://github.com/python-pillow/Pillow/blob/9923531742726419732618c6f2aef0bb8c21e259/src/PIL/XpmImagePlugin.py#L106

Neither does load_seek(). For example, https://github.com/python-pillow/Pillow/blob/9923531742726419732618c6f2aef0bb8c21e259/src/PIL/FtexImagePlugin.py#L105 https://github.com/python-pillow/Pillow/blob/9923531742726419732618c6f2aef0bb8c21e259/src/PIL/IcoImagePlugin.py#L342