feat: add message IDs to private group messages

[JFreegman]

This change is 

[codecov]

Codecov Report

Attention: Patch coverage is 65.00000% with 14 lines in your changes are missing coverage. Please review.

Project coverage is 73.13%. Comparing base (99e0bcc) to head (7b1db6a).

Files	Patch %	Lines
toxcore/tox.c	30.76%	9 Missing ⚠️
toxcore/events/group_private_message.c	54.54%	5 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2727      +/-   ##
==========================================
+ Coverage   73.05%   73.13%   +0.07%     
==========================================
  Files         149      149              
  Lines       30499    30516      +17     
==========================================
+ Hits        22282    22317      +35     
+ Misses       8217     8199      -18     

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[Green-Sky]

you need to adjust the event here:

c-toxcore/other/event_tooling/generate_event_c.cpp

Lines 744 to 761 in b3c3c49

	"Group_Message",
	{
	EventTypeTrivial{"uint32_t", "group_number"},
	EventTypeTrivial{"uint32_t", "peer_id"},
	EventTypeTrivial{"Tox_Message_Type", "type"},
	EventTypeByteRange{"message", "message_length", "length"}, // the latter two are ideally the same
	EventTypeTrivial{"uint32_t", "message_id"},
	}
	},
	{
	"Group_Private_Message",
	{
	EventTypeTrivial{"uint32_t", "group_number"},
	EventTypeTrivial{"uint32_t", "peer_id"},
	EventTypeTrivial{"Tox_Message_Type", "type"},
	EventTypeByteRange{"message", "message_length", "length"}, // the latter two are ideally the same
	}
	},

[Green-Sky]

@JFreegman commit message is wrong, needs to be messages, not packets.

[Green-Sky]

commit message is wrong