Fix/field default

[ThirVondukr]

This PR changes value of default and default_factory to dataclasses.MISSING so strawberry.UNSET could be used to create optional fields in input types.

Types of Changes

• [ ] Core
• [x] Bugfix
• [ ] New feature
• [x] Enhancement/optimization
• [ ] Documentation

Checklsit

• [x] My code follows the code style of this project.
• [ ] My change requires a change to the documentation.
• [ ] I have updated the documentation accordingly.
• [x] I have read the CONTRIBUTING document.
• [ ] I have added tests to cover my changes.
• [ ] I have tested the changes and verified that they work and don't break anything (as well as I can manage).

[codecov[bot]]

Codecov Report

Merging #2089 (29c58a2) into main (a051eb8) will decrease coverage by 0.06%. The diff coverage is n/a.

@@            Coverage Diff             @@
##             main    #2089      +/-   ##
==========================================
- Coverage   98.09%   98.03%   -0.07%     
==========================================
  Files         152      152              
  Lines        6095     6094       -1     
  Branches     1160     1160              
==========================================
- Hits         5979     5974       -5     
- Misses         58       60       +2     
- Partials       58       60       +2