Implement submission memfd output

[quantum5]

This makes non-interactive problems output to memfd.

[codecov]

Codecov Report

Attention: Patch coverage is 82.35294% with 6 lines in your changes missing coverage. Please review.

Project coverage is 50.77%. Comparing base (315ede5) to head (d5a3a24).

Files with missing lines	Patch %	Lines
dmoj/graders/standard.py	81.25%	6 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           master    #1198       +/-   ##
===========================================
- Coverage   82.56%   50.77%   -31.79%     
===========================================
  Files         146      146               
  Lines        5666     5692       +26     
===========================================
- Hits         4678     2890     -1788     
- Misses        988     2802     +1814     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.