quality-of-life: Improve local development tooling

[sebrandon1]

This PR updates the Makefile with .PHONY targets, better error handling for deploy/undeploy, and adds README.md sections on cleanup, tests, and linting.

Makefile Enhancements:

• Added .PHONY declarations to multiple targets (local-run, build-operator, build, run, image-build, image-push, deploy, undeploy, test-e2e-wait-for-stable-state, test-e2e-debug-cluster, lint) to ensure proper execution and avoid conflicts with files of the same name. [1] [2] [3] [4] [5]

• Improved the deploy target to create the cert-manager-operator namespace if it does not exist, ensuring smoother deployment.

• Enhanced the undeploy target to ignore not-found errors when deleting resources, improving robustness.

• Added a check in the lint target to ensure golangci-lint is installed before running, providing a clearer error message if it is missing.

Documentation Updates:

• Added a "Cleaning up the deployment" section in README.md, explaining how to remove the Cert Manager Operator and its associated resources using make undeploy.

• Introduced a "Running tests locally" section in README.md, detailing how to execute unit tests and generate a coverage report.

• Added a "Linting the code" section in README.md, describing how to run make lint to check for linting issues using golangci-lint.

[openshift-ci]

[APPROVALNOTIFIER] This PR is NOT APPROVED

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[openshift-ci]

@sebrandon1: The following test failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
ci/prow/e2e-operator-tech-preview	6f8a1be	link	false	/test e2e-operator-tech-preview

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