Copilot/add pynfe group k support

[claudio-mas]

This pull request adds support for product traceability and specific medication details in the Nota Fiscal entities and their XML serialization. The main changes are the introduction of the NotaFiscalRastro class for traceability, new medication-specific fields, and updates to the serialization logic to handle these additions.

Product Traceability Support:

• Added the NotaFiscalRastro class to represent product traceability information (e.g., lot number, quantity, manufacturing and expiration dates, aggregation code) in pynfe/entidades/notafiscal.py.
• Updated the NotaFiscalProduto class to include a rastro attribute (list of traceability records) and an adicionar_rastro method for managing traceability data.
• Modified the _serializar_produto_servico function in pynfe/processamento/serializacao.py to serialize the new traceability (rastro) information into the XML output.

Medication-Specific Fields:

• Added new fields to NotaFiscalProduto for medication details: med_cProdANVISA, med_xMotivoIsencao, and med_vPMC.
• Updated the serialization logic in _serializar_produto_servico to include the medication group (med) and its fields in the XML when applicable.