Image: Deprecate OneOf implementation for cacheFrom

[guineveresaenger]

Currently, the cacheFrom input on DockerBuild can either be a boolean or aCacheFrom supporting type which contains stages, a list of strings. This is implemented on current master branch as well, but it adds a lot of extra input handling to the provider logic.

Rather than allow users to set a boolean or a CacheFrom type with stages, we should remove the boolean option.
Instead, we will allow for cacheFrom to be a list of strings and add logic to determine either reasonable default (to handle the current true case) or whether this field is not set (to handle the current false case).

[pulumi-bot]

Cannot close issue without required labels: kind/