DM-46601: Use nanoseconds for ingest_date for new repos

[andy-slac]

Checklist

• ran Jenkins
• added a release note for user-visible changes to doc/changes
• (if changing dimensions.yaml) make a copy of dimensions.yaml in configs/old_dimensions

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 89.67%. Comparing base (9600402) to head (35d2c7f).
Report is 4 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1091      +/-   ##
==========================================
- Coverage   89.69%   89.67%   -0.02%     
==========================================
  Files         361      361              
  Lines       47306    47306              
  Branches     9720     9720              
==========================================
- Hits        42429    42424       -5     
- Misses       3498     3504       +6     
+ Partials     1379     1378       -1     

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

[timj]

Maybe add a misc news fragment?