Abstract the internal storage of the NamedAttributeList into a new attribute...

Abstract the internal storage of the NamedAttributeList into a new attribute, DictionaryAttr. This attribute maintains a sorted list of NamedAttributes. This will allow for operations/functions to maintain sub dictionaries of attributes.

    The syntax is the same as top level attribute dictionaries:
       {sub_dictionary: {fn: @someFn, boolAttr: true}}

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PiperOrigin-RevId: 250898950