(fix)[avro] Use correct DatumWriter constructor

[RustedBones]

Use correct avro writer constructor that would load the generated model with conversions.

Setup CI to test scio-avro with latest version on main

Fix #5331

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 75.00000% with 1 lines in your changes are missing coverage. Please review.

Project coverage is 61.12%. Comparing base (d235906) to head (759b4ae).

Files	Patch %	Lines
...scala/com/spotify/scio/avro/AvroDatumFactory.scala	75.00%	1 Missing :warning:

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #5371   +/-   ##
=======================================
  Coverage   61.11%   61.12%           
=======================================
  Files         304      304           
  Lines       10927    10927           
  Branches      775      751   -24     
=======================================
+ Hits         6678     6679    +1     
+ Misses       4249     4248    -1     

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