fix(pytest): use python proxy framework to isolate nodes instead of unix utilities

[birchmd]

The goal of the local_network stress test is to ensure the network functions well under the condition that a random node occasionally loses contact with the rest of the network (i.e. experiences a "local network failure"). Previously this test was implemented by restricting access to network interfaces of specific process ids at the OS level. This solution was a little hacky, platform dependent, and not entirely reliable. We now have a proxy framework as part of pytest which is exactly meant to change (or drop) messages between nodes. We now make use of this framework in the local_network stress test instead of using the Unix utilities.

[gitpod-io]

[birchmd]

python tests/stress/stress.py 3 3 3 0 staking transactions local_network

@SkidanovAlex could you try running this locally? For me I find that the test fails after some time because of timeout trying to access the node's RPC even though I increased the timeout to 5s in this PR. I'm not sure if this is revealing a bug in the node or if the problem is my machine is somehow slow.

[codecov]

Codecov Report

Merging #3076 into master will decrease coverage by 0.05%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #3076      +/-   ##
==========================================
- Coverage   87.49%   87.44%   -0.06%     
==========================================
  Files         212      212              
  Lines       41185    41185              
==========================================
- Hits        36036    36013      -23     
- Misses       5149     5172      +23     

Impacted Files	Coverage Δ
neard/tests/stake_nodes.rs	85.66% <0.00%> (-12.11%)	⬇️
chain/client/src/sync.rs	86.21% <0.00%> (-1.52%)	⬇️
chain/client/tests/bug_repros.rs	94.03% <0.00%> (-1.33%)	⬇️
chain/network/tests/routing.rs	99.37% <0.00%> (-0.63%)	⬇️
chain/chain/src/doomslug.rs	99.22% <0.00%> (-0.52%)	⬇️
chain/chain/src/store.rs	86.87% <0.00%> (-0.46%)	⬇️
chain/network/src/routing.rs	92.81% <0.00%> (-0.20%)	⬇️
chain/client/src/view_client.rs	68.29% <0.00%> (-0.19%)	⬇️
chain/client/tests/process_blocks.rs	89.71% <0.00%> (-0.16%)	⬇️
chain/chain/src/chain.rs	88.51% <0.00%> (-0.11%)	⬇️
... and 9 more

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[SkidanovAlex]

python tests/stress/stress.py 3 3 3 0 staking transactions local_network

@SkidanovAlex could you try running this locally? For me I find that the test fails after some time because of timeout trying to access the node's RPC even though I increased the timeout to 5s in this PR. I'm not sure if this is revealing a bug in the node or if the problem is my machine is somehow slow.

Locally also hit RPC timeouts.

[birchmd]

Closing, changes were included in #3175