install: add spec for control plane installation

[mayankshah1607]

This test is responsible for installing and verifying the control plane on the cluster.The control plane installation must be the first test that must take place in the conformance validation process. The tests must be declared under a separate spec in spec/install.

This test suite consists of the following checks:

• Issue a linkerd install command and pipe output to kubectl, and validate the exit code on the command
• Parse and verify the output of linkerd check
• Verifying state of control plane components