Move mock_logger from testutil to logger

[srijan-27]

• mocklogger was present as part of testutil package which isn't ideal.
• Hence, moved mocklogger in logging package itself.
• Although to fix the cyclic dependency between logging and service packages, have created a new sub package remotelogger.
  NOTE: NewRemoteLogger is renamed to New, since now it is part of remotelogger package.
• Closes issue: MockLogger should be in logging package and not in testutil #540

Checklist:

• I have formatted my code using goimport and golangci-lint.
• All new code is covered by unit tests.
• This PR does not decrease the overall code coverage.
• I have reviewed the code comments and documentation for clarity.

[vikash]

Shifting the mockLogger to a sub package does not really change anything. Log level for examples are not the same.

[aryanmehrotra]

We can see separately if we even want to use MockLogger, as NewLogger should also be good to use!