Consider k8s service account name from evaluated local parameter

[sig-abyreddy]

Module supports providing a custom name for kubernetes service account through k8s_sa_name variable. But internally this value is not considered for kubernetes service account resource.

k8s_given_name has evaluated value for service account name under locals. Using this value will respect custom input from the user.

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[sig-abyreddy]

@googlebot I signed it!

[morgante]

Test failure is unrelated.

[sig-abyreddy]

Thank for accepting the MR @morgante