Fix double-free throughout amqp_definitions caught by MSRC

This is related to issue MSRC84965  (work item 186232).

The bugs identified by MSRC in open_get_offered_capabilities are correct.
open_get_offered_capabilities is implemented in amqp_definitions.c, which is autogenerated from amqp_definitions_c.tt.
amqp_definitions_c.tt is also used to autogerate functions for other AMQP composite types.
By fixing amqp_definitions_c.tt (function in lines 317 to 494) this double-free bug pattern is being addressed for:
- open_get_outgoing_locales
- open_get_incoming_locales
- open_get_offered_capabilities
- open_get_desired_capabilities
- begin_get_offered_capabilities
- begin_get_desired_capabilities
- attach_get_offered_capabilities
- attach_get_desired_capabilities
- sasl_mechanisms_get_sasl_server_mechanisms
- source_get_outcomes
- source_get_capabilities
- target_get_capabilities