Move parameters and conversion functions to their own packages

[julianKatz]

What type of PR is this?

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/kind api-change
/kind bug
/kind cleanup
/kind design
/kind documentation
/kind failing-test
/kind feature
/kind flake

What this PR does / why we need it:

This PR is a follow-up to #2186.

This PR moves the parsing of parameters into their own package: pkg/parameters. This is a lot of logic and worthy of its own package.

Along the way, I found that pkg/common had a number of conversion helper functions (Convert.*) that were public and occasionally used by both parameters.go and other files, and sometimes only parameters.go. Several of them also had their own unit tests already. Thus, I thought this was also worthy of its own package. This PR thus adds pkg/convert.

Which issue(s) this PR fixes:

Fixes #

Special notes for your reviewer:

Does this PR introduce a user-facing change?:

NONE

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[k8s-ci-robot]

@julianKatz: 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-gcp-compute-persistent-disk-csi-driver-unit	eac2b7f	link	true	/test pull-gcp-compute-persistent-disk-csi-driver-unit
pull-gcp-compute-persistent-disk-csi-driver-e2e-arm	eac2b7f	link	false	/test pull-gcp-compute-persistent-disk-csi-driver-e2e-arm
pull-gcp-compute-persistent-disk-csi-driver-e2e	eac2b7f	link	true	/test pull-gcp-compute-persistent-disk-csi-driver-e2e
pull-gcp-compute-persistent-disk-csi-driver-sanity	eac2b7f	link	true	/test pull-gcp-compute-persistent-disk-csi-driver-sanity
pull-gcp-compute-persistent-disk-csi-driver-verify	eac2b7f	link	true	/test pull-gcp-compute-persistent-disk-csi-driver-verify
pull-gcp-compute-persistent-disk-csi-driver-e2e-windows-2019	eac2b7f	link	false	/test pull-gcp-compute-persistent-disk-csi-driver-e2e-windows-2019
pull-gcp-compute-persistent-disk-csi-driver-e2e-windows-2022	eac2b7f	link	false	/test pull-gcp-compute-persistent-disk-csi-driver-e2e-windows-2022
pull-gcp-compute-persistent-disk-csi-driver-kubernetes-integration	eac2b7f	link	true	/test pull-gcp-compute-persistent-disk-csi-driver-kubernetes-integration

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