Handle Sensitive Zarf Vars

[TristanHoladay]

Zarf Variables can be specified as sensitive in a Zarf package yaml. Ensure that we check if any Zarf vars are sensitive and if so mask them in uds output.

Some considerations:
This requires loading the zarf package metadata, which we can use loadPackage() from inspect.go for. That means we're now loading packages at two points in the deployment flow -- pre-deploy views and actual deployment.

Alternate Options:
We don't display any Zarf vars and their values in the pre-deploy view. When the bundle deploys, each package definition with its vars and their current values are displayed and Zarf already handles masking the sensitive values in that output.