`attributes_sort` failes when attribute does not have a `requirement_level`

[michaelvanstraten]

Describe the bug
The attributes_sort minijinja filter fails when one (or multiple) attributes are missing the requirement_level.

To Reproduce
Steps to reproduce the behavior:

Run the v2 forge via weaver registry generate --v2 and make use of the attribute_sort filter on the attributes field of a group.

Expected behavior
I expect the requirement level on an attribute to default to recommended like the event, metric and span signals do here.

Additional context

None yet

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