config: Add GoMemLimit config option and use with 10-node test

[ohill]

Summary

This adds a config option GoMemLimit for a soft memory limit like GOMEMLIMIT. It uses it for TestPartitionHalfOffline which runs 10 nodes (TenNodesDistributedMultiWallet.json) for 1GB each. It also uses it for TestSendSigsAfterCatchpointCatchup which starts 3 nodes and has one generate a catchpoint snapshot for the others.

Test Plan

TestPartitionHalfOffline should run 10 nodes without using as much memory, and TestSendSigsAfterCatchpointCatchup should also use less memory.

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 2 lines in your changes are missing coverage. Please review.

Project coverage is 56.00%. Comparing base (dfd95ff) to head (e0cb8d0).

Files	Patch %	Lines
cmd/algod/main.go	0.00%	2 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #5975   +/-   ##
=======================================
  Coverage   56.00%   56.00%           
=======================================
  Files         481      481           
  Lines       67646    67648    +2     
=======================================
+ Hits        37883    37887    +4     
- Misses      27197    27200    +3     
+ Partials     2566     2561    -5     

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[gmalouf]

I think a config option is reasonable enough, understanding we may want to later remove if Golang changes the expected behavior/approach.

[algorandskiy]

LGTM but lets merge after p2p branch since it also adds v34 config, and rebasing this smaller PR will be easier.

[algorandskiy]

Well although feature/p2p has a conflict so requires manual remerge anyway, lets get it merged.