Apply dataclass transform to AtomMeta

[MatthieuDartiailh]

All members are declared as field specifiers which allow to use them in addition of an annotation.

I am considering adding other field specifiers to:

• allow to tag a member without needing to rely on a member
• allow to specify a default value factory
• I would like to be able to specify arg/kwargs for Typed/Instance but this cannot be statically validated...

I am considering something along the following lines to stay close to the existing syntax.

class A(Atom):

    a: int = member(default=1).tag(a=1)
  

Any opinion @frmdstryr

Closes #173

[frmdstryr]

I still use the "old" method of just using members directly but this looks fine to me.

[codecov]

Codecov Report

Merging #210 (8b8e513) into main (d6a1b11) will decrease coverage by 1.74%.
The diff coverage is 83.80%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #210      +/-   ##
==========================================
- Coverage   97.67%   95.93%   -1.74%     
==========================================
  Files          24       24              
  Lines        1075     1181     +106     
  Branches      174      200      +26     
==========================================
+ Hits         1050     1133      +83     
- Misses         12       29      +17     
- Partials       13       19       +6