[*] migrate all helpers to testutil

[0xgouda]

• builds on top of [+] add new testutil package #1064 and migrates all remaining helpers/mocks to testutil package.

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TODO:

• Fix race condition that may originate from using SetupRPCServers() in tests multiple times.
• Add more tests to increase test coverage.

[coveralls]

Pull Request Test Coverage Report for Build 19972143452

Details

• 39 of 85 (45.88%) changed or added relevant lines in 3 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-0.5%) to 73.512%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
internal/testutil/mocks.go	39	42	92.86%
internal/testutil/common.go	0	18	0.0%
internal/testutil/setup.go	0	25	0.0%

Totals
Change from base Build 19968648019:	-0.5%
Covered Lines:	3816
Relevant Lines:	5191

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💛 - Coveralls