[WIP] Add GPU Support to CAPG

[sayantani11]

What type of PR is this?

What this PR does / why we need it:
Support instances of "A2" family as well as all five GPUs available with "N1" instances. Regular and preemptible instances. Does not support GPUs for graphics workloads.

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged):
Fixes #289

Special notes for your reviewer:

Please confirm that if this PR changes any image versions, then that's the sole change this PR makes.

TODOs:

• squashed commits
• includes documentation
• adds unit tests

Release note:

Enables GPU support to CAPG

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

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[k8s-ci-robot]

@sayantani11: The following tests failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
pull-cluster-api-provider-gcp-verify	9dae5f3	link	true	/test pull-cluster-api-provider-gcp-verify
pull-cluster-api-provider-gcp-build	9dae5f3	link	true	/test pull-cluster-api-provider-gcp-build
pull-cluster-api-provider-gcp-test	9dae5f3	link	true	/test pull-cluster-api-provider-gcp-test
pull-cluster-api-provider-gcp-make	9dae5f3	link	true	/test pull-cluster-api-provider-gcp-make
pull-cluster-api-provider-gcp-e2e-test	9dae5f3	link	true	/test pull-cluster-api-provider-gcp-e2e-test

Full PR test history. Your PR dashboard. Please help us cut down on flakes by linking to an open issue when you hit one in your PR.

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[k8s-ci-robot]

@sayantani11: PR needs rebase.

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