Adding a test for admin_commands (cadence-workflow#6414)

* Adding a test for admin_commands

For now it is a test for a single function: ResetQueue
Inroducing clitest package as a helper to write cli tests.
Previously we were mistakenly overriding flags in flag.FlagSet which
does not align with `context.IsSet()` - it thinks user did not provide
an argument.

* Converging admin_cluster_commands_test.go

To follow a new, shorter approach with newCLITestData/clitest.

* Converging admin_task_list_commands_test.go

To follow a new, shorter approach with newCLITestData/clitest.