attrs: use sugar syntax for factory

[skshetry]

There are three ways to set factory in attrs:

1. What is being done in the PR.

@define
class Klass:
  attr: list = field(default=Factory(list))

2. Using factory kwarg, which is a sugar for above.

@define
class Klass:
  attr: list = field(factory=list)

3. Another sugar for above.

@define
class Klass:
  attr: list = Factory(list)

1. is verbose, but I prefer 2).

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (a535b4b) 63.70% compared to head (eb93189) 63.74%.
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #487      +/-   ##
==========================================
+ Coverage   63.70%   63.74%   +0.03%     
==========================================
  Files          61       61              
  Lines        4177     4173       -4     
  Branches      714      713       -1     
==========================================
- Hits         2661     2660       -1     
+ Misses       1368     1367       -1     
+ Partials      148      146       -2     

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