DM-54979: Protect against writing : into file templates

[timj]

These were turning up in group records. Also add additional special characters that might mess up a file sytem.

Checklist

• ran Jenkins
• added a release note for user-visible changes to doc/changes
• (if changing dimensions.yaml) make a copy of the updated dimensions.yaml in configs/old_dimensions and update the list in doc/lsst.daf.butler/dimensions.rst

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 89.62%. Comparing base (4a958a8) to head (f15a680).
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1374   +/-   ##
=======================================
  Coverage   89.62%   89.62%           
=======================================
  Files         373      373           
  Lines       50772    50776    +4     
  Branches     5913     5913           
=======================================
+ Hits        45502    45506    +4     
  Misses       3880     3880           
  Partials     1390     1390           

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