Refactor IsPowerVSZoneSupportsPER() to use interface

[Karthik-K-N]

/kind feature
/area provider/ibmcloud

Describe the solution you'd like
[A clear and concise description of what you want to happen.]

Currently IsPowerVSZoneSupportsPER() is directly calling dataceter client to get details, It will be problem while implementing UT so consider refactoring it to use interfaces which will help in mocking.

Anything else you would like to add:
[Miscellaneous information that will assist in solving the issue.]

[Karthik-K-N]

/assign @Shilpa-Gokul

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/assign @Shilpa-Gokul

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[Shilpa-Gokul]

/assign @Shilpa-Gokul