When Expression.__init__() overrides make use of *args, **kwargs
captures their argument values are respectively bound as a tuple and
dict instances. These composite values might themselves contain values
that require special identity treatments such as Concat(output_field)
as it's a Field instance.
Refs #30628 which introduced bound Field differentiation but lacked
argument captures handling.
Thanks erchenstein for the report.
Backport of df2c4952df6d93c575fb8a3c853dc9d4c2449f36 from main
