Consider aligning asset handling to the pulumi-terraform-bridge

[komalali]

We added handling for the Environment.Yaml property, which is of an asset type, to expand the asset during Check into its string form. In the future, we should consider aligning our asset handling with how the bridge handles it, since it offers more flexibility for path-based properties.

From @pgavlin: I think that this will likely work in the case that the underlying resource expects a literal. in the case the underlying resource expects a path, things get muddier. assets are a bit ill-considered, but part of what they're intended to address is the case of properties that accept paths, as paths may (will) differ from machine to machine,

The bridge walks the old inputs and records which property values were assets, then walks the new state and turns anything that was an asset back into an asset.

Links to source:

• Relevant comment: https://github.com/pulumi/pulumi-terraform-bridge/blob/master/pkg/tfbridge/schema.go#L135-L136
• Relevant type: https://github.com/pulumi/pulumi-terraform-bridge/blob/master/pkg/tfbridge/schema.go#L189-L191
• Relevant bit of read: https://github.com/pulumi/pulumi-terraform-bridge/blob/master/pkg/tfbridge/provider.go#L1277-L1282