Add e2e tests for Operator

[VaishnaviHire]

Description

This PR introduces e2e testing to the operator. It tests following use cases:

• Validating Operator Deployment
• Creation of KfDef
• Validating labels and annotations in the managed resources
• Validating that changes to the managed resources are reverted
• Validating deletion of KfDef and its managed resources

How Has This Been Tested?

Testing Instructions: Run-e2e section in README.md

Note:

There are additional use cases that are more involved and can be added to this test-suite as part of follow-up PRs/issues

• The commits are squashed in a cohesive manner and have meaningful messages.
• Testing instructions have been added in the PR body (for PRs involving changes that are not immediately obvious).
• The developer has manually tested the changes and verified that the changes work

[VaishnaviHire]

Output from local run:

 ✗ make e2e-test
warning: GOPATH set to GOROOT (/Users/vhire/go/go1.18.9) has no effect
go test ./tests/e2e/ -run ^TestOdhOperator -v --kf-namespace=odh-e2e-test "--skip-deletion=false" 
warning: GOPATH set to GOROOT (/Users/vhire/go/go1.18.9) has no effect
=== RUN   TestOdhOperator
=== RUN   TestOdhOperator/validate_controllers
=== RUN   TestOdhOperator/validate_controllers/Validate_KfDef_controller
=== RUN   TestOdhOperator/validate_controllers/Validate_CRDs_owned_by_the_operator
=== RUN   TestOdhOperator/create
=== RUN   TestOdhOperator/create/e2e-test
=== RUN   TestOdhOperator/create/e2e-test/Creation_of_KfDef_instance
=== RUN   TestOdhOperator/create/e2e-test/Validate_deployed_applications
=== RUN   TestOdhOperator/create/e2e-test/Validate_deployed_applications/Validate_deployments_for_application_odh-dashboard
2023/02/27 15:23:38 waiting for application deployments to be in Ready state.
2023/02/27 15:23:48 waiting for application deployments to be in Ready state.
2023/02/27 15:23:58 waiting for application deployments to be in Ready state.
2023/02/27 15:24:08 waiting for application deployments to be in Ready state.
2023/02/27 15:24:18 waiting for application deployments to be in Ready state.
2023/02/27 15:24:28 waiting for application deployments to be in Ready state.
2023/02/27 15:24:38 waiting for application deployments to be in Ready state.
=== RUN   TestOdhOperator/create/e2e-test/Validate_KfDef_Annotation_is_added
=== RUN   TestOdhOperator/create/e2e-test/Validate_Controller_Reverts_Updates
=== RUN   TestOdhOperator/delete
=== RUN   TestOdhOperator/delete/e2e-test
=== RUN   TestOdhOperator/delete/e2e-test/KfDef_Deletion
=== RUN   TestOdhOperator/delete/e2e-test/Application_Resource_Deletion
=== RUN   TestOdhOperator/delete/e2e-test/Application_Resource_Deletion/Validate_deletion_for_application_odh-dashboard
--- PASS: TestOdhOperator (209.04s)
    --- PASS: TestOdhOperator/validate_controllers (63.04s)
        --- PASS: TestOdhOperator/validate_controllers/Validate_KfDef_controller (10.05s)
        --- PASS: TestOdhOperator/validate_controllers/Validate_CRDs_owned_by_the_operator (50.21s)
    --- PASS: TestOdhOperator/create (113.09s)
        --- PASS: TestOdhOperator/create/e2e-test (110.45s)
            --- PASS: TestOdhOperator/create/e2e-test/Creation_of_KfDef_instance (10.10s)
            --- PASS: TestOdhOperator/create/e2e-test/Validate_deployed_applications (80.05s)
                --- PASS: TestOdhOperator/create/e2e-test/Validate_deployed_applications/Validate_deployments_for_application_odh-dashboard (80.05s)
            --- PASS: TestOdhOperator/create/e2e-test/Validate_KfDef_Annotation_is_added (0.15s)
            --- PASS: TestOdhOperator/create/e2e-test/Validate_Controller_Reverts_Updates (20.15s)
    --- PASS: TestOdhOperator/delete (32.90s)
        --- PASS: TestOdhOperator/delete/e2e-test (30.25s)
            --- PASS: TestOdhOperator/delete/e2e-test/KfDef_Deletion (0.10s)
            --- PASS: TestOdhOperator/delete/e2e-test/Application_Resource_Deletion (30.15s)
                --- PASS: TestOdhOperator/delete/e2e-test/Application_Resource_Deletion/Validate_deletion_for_application_odh-dashboard (30.15s)
PASS
ok      github.com/opendatahub-io/opendatahub-operator/tests/e2e        209.676s

[LaVLaS]

/lgtm

Running make deploy e2e-test worked for me with no issues

[openshift-ci]

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