Rename LighterWriter's arguments

[ibro45]

🚀 Feature Request

write_dir -> save_dir, write_interval -> interval, write_format -> ?. Would be good not to override the built-in format. Yes, we are overriding the built-in input throughout the code, but the community's used to it because PyTorch does that. Furthermore, almost no one ever uses input(), whereas string formatting with format() isn't uncommon.

🔈 Motivation

LighterWriter's name says it's a writer, no need to repeat that in the arguments.

🛰 Alternatives

Override the built-in format, or come up with a synonym for format.

[surajpaib]

I don't necessarily see the issue with using format. The format used for strings is a method for the string class and should be available irrespective of us using the name in the class. We will never actually be overriding it.

Given the context, I also think it isn't confusing to use it as it's obvious we are not referring to the method format of string