network: increase max incoming connections limit

[algorandskiy]

Summary

According to the latest measurement a single connection consumes about 1 MiB of RAM (calculated 600 KiB measured lower bound is 800 KiB, upper bound is 1.5 MiB).
Setting IncomingConnectionsLimit to 2400 should have a total memory footprint of 3.6 GiB.
Also decreased MaxConnectionsPerIP to 15 as a best guess based on a fact only fraction of nodes report hitting this limit.

Test Plan

Existing tests

[gmalouf]

I'd like to see a change here paired with lowering the per host connection limit (perhaps to 10) - know that is under discussion.

[codecov]

Codecov Report

Merging #5018 (07552db) into master (5d38a15) will decrease coverage by 0.00%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #5018      +/-   ##
==========================================
- Coverage   53.62%   53.62%   -0.01%     
==========================================
  Files         432      432              
  Lines       54060    54060              
==========================================
- Hits        28991    28990       -1     
  Misses      22824    22824              
- Partials     2245     2246       +1     

Impacted Files	Coverage Δ
config/localTemplate.go	43.75% <ø> (ø)
crypto/merkletrie/trie.go	66.42% <0.00%> (-2.19%)	⬇️
crypto/merkletrie/node.go	91.62% <0.00%> (-1.87%)	⬇️
catchup/service.go	69.08% <0.00%> (+0.48%)	⬆️
ledger/acctonline.go	79.16% <0.00%> (+0.52%)	⬆️
ledger/tracker.go	75.10% <0.00%> (+0.84%)	⬆️

📣 We’re building smart automated test selection to slash your CI/CD build times. Learn more