DM-47976: Support conversion field in file template format strings

[tgoldina]

A fix to support type conversion in file template format strings. For example, the conversion specifier !s in a format string like {healpix!s:.2s} converts a numeric field healpix into a string before applying additional formatting.

The modified unit test, which previously produced a ValueError: Unknown format code 's' for object of type 'int', now passes.

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

[timj]

Can you add a test please?

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 89.46%. Comparing base (0155486) to head (8788edb).
Report is 2 commits behind head on main.

✅ All tests successful. No failed tests found.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1127   +/-   ##
=======================================
  Coverage   89.46%   89.46%           
=======================================
  Files         366      366           
  Lines       48774    48779    +5     
  Branches     5907     5908    +1     
=======================================
+ Hits        43637    43642    +5     
  Misses       3721     3721           
  Partials     1416     1416           

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[andy-slac]

Looks great.