Add reverseproxy tls certificate in New API client

[AkshaySainiDell]

Description

This PR includes:

• Add support for reverseproxy tls certificate loading in while creating New API client.
• UT coverage for pkg - api

GitHub Issues

List the GitHub issues impacted by this PR:

GitHub Issue #
dell/csm#1571

Checklist:

• Have you run format,vet & lint checks against your submission?
• Have you made sure that the code compiles?
• Did you run the unit & integration tests successfully?
• Have you maintained at least 90% code coverage?
• Have you commented your code, particularly in hard-to-understand areas
• Have you done corresponding changes to the documentation
• Did you run tests in a real Kubernetes cluster?
• Backward compatibility is not broken

How Has This Been Tested?

• Deployed the driver using Helm with reverse proxy configured as a sidecar and skipCertificateValidation set to false, then successfully executed the cert-csi scale test.
• Deployed the driver using Helm with reverse proxy configured as a sidecar and skipCertificateValidation set to true, then successfully executed the cert-csi scale test.
• Deployed the driver using Helm with reverse proxy configured as a deployment and skipCertificateValidation set to false, then successfully executed the cert-csi scale test.
• Deployed the driver using Helm with reverse proxy configured as a deployment and skipCertificateValidation set to true, then successfully executed the cert-csi scale test.