Add missing unit tests for p2p

[ishantiw]

Description

There are lots of tests missing in p2p and peer modules and also few tests in others. Add all the relevant test cases.

Below is the list of modules that are missing test cases.

• validation.ts related issue Add missing unit tests of validation in lisk-p2p lisk-elements#1038
• errors.ts related issue Add missing unit tests for custom errors in lisk-p2p lisk-elements#1043
• peer/base.ts Add unit test coverage for P2P base peer file #4223 @diego-G Add unit test for P2P base peer file - Closes #4223 #4258
• peer/inbound.ts Add unit test coverage for P2P inbound peer file #4224 @diego-G Add unit tests for P2P Inbound peer class - Closes #4224 #4296
• peer/outbound.ts Add unit test coverage for P2P outbound peer file  #4225 @diego-G Add unit tests for P2P Outbound peer class - Closes #4225 #4277
• peer_directory/peer_book.ts Add unit test coverage for P2P peer_book file #4226
• peer_directory/ Add unit test coverage for P2P peer directory folder  #4227 @diego-G Increase unit test coverage across P2P peer book - Closes #4227 #4377
• peer_pool.ts Add unit test coverage for P2P peer pool file #4229 @mitsujutsu Add unit test coverage for P2P PeerPool - Closes #4229 #4357
• p2p_request.ts Add unit test coverage for P2P request file #4230 @jondubois
• p2p.ts Add unit test coverage for main P2P file #4228
• Move unnecessary tests from integration tests to unit tests

[shuse2]

Closing since All of the critical unit tests are already covered