feat: allow for larger incoming NGC packets

[zoff99]

This change is 

[JFreegman]

What's the purpose of this and when would it be applicable?

[codecov]

Codecov Report

Attention: 6 lines in your changes are missing coverage. Please review.

Comparison is base (8792672) 74.51% compared to head (d9095eb) 74.43%.
Report is 1 commits behind head on master.

❗ Current head d9095eb differs from pull request most recent head cd34b60. Consider uploading reports for the commit cd34b60 to get more accurate results

Files	Patch %	Lines
toxcore/tox.c	0.00%	4 Missing ⚠️
toxcore/group_chats.c	33.33%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2380      +/-   ##
==========================================
- Coverage   74.51%   74.43%   -0.08%     
==========================================
  Files          87       87              
  Lines       26241    26243       +2     
==========================================
- Hits        19554    19535      -19     
- Misses       6687     6708      +21     

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[iphydf]

It might make sense to make toxcore generally more accepting of incoming packets up to some size (e.g. 1500 bytes). On Ethernet, we'll never get that kind of packet size, but it's not bad to be lenient on the inbound packet size. We still need some limit to avoid DoS, but 1500 seems reasonable for any packet processor functions.

[iphydf]

Incoming packet sizes should generally be quite accepting. We should not allow arbitrary sizes (because DoS), but something upwards of MTU makes sense.

[iphydf]

Reviewed 1 of 3 files at r1, 3 of 3 files at r2, all commit messages.
Reviewable status: complete! 1 of 1 approvals obtained