Enhancement: Implement retrieval and calculation of prices info using GCP CloudBilling API

[dm3ch]

Empediment from: #31

GCP doesn't have an API that tells you how much the VM type costs.
But they have an https://cloud.google.com/billing/docs/reference/rest/v1/services.skus which is really hard to use, but can provide information how does VM parts costs (CPU / RAM / etc).

So to not to bring too complex pricing logic at the beginning we leveraged already calculated pricing data provided by https://github.com/Cyclenerd/google-cloud-pricing-cost-calculator project.

It seems it would make sense to try to reimplement runtime price retrieval to the calculation of instance prices on Karpenter provider side (this project).
Also rewriting initial prices to use the own calculation logic, if possible.

P.S. Don't forget about GPU, sustainable usage discount, disks in calculation, custom machine types

[jwcesign]

Karpenter doesn't need disk pricing information actually.
Sustainable usage discount, I guess it should be handled in karpenter core.
We will back after MVP demo.

[dm3ch]

Yeah, let's postpone it until there is a working MVP.

Regarding disks, I meant that we need to calculate disk sizes in case node have local disks as part of instance type. But actually I haven't checked if there're instance types with predefined disks.

Regarding the sustainable usage discount, as far as I understand,the following RFC is going to do some for that. I haven't read it fully yet, and didn't understood how it implements default cloud discounts (not user specific). Cause google have sustainable usage discount for specific node types (when you're selecting instance type during creation). But maybe I haven't read the google doc and don't fully understand how it meant to work.

Also just added info that we need to think latter about custom instance types as well....