Implement text interpolation

Problem

We want to support array type inputs and the use of !reference with interpolation. The existing hash interpolation process can not do that without updates.

Proposed Solution

Switch to a text interpolation process, as defined by a spike !136075 (closed)

Implementation Table

Step	Link
Add text interpolation classes to Interpolation module	!138083 (merged)
Introduce Interpolation::Params	!140344 (merged)
Update Yaml::Loader to use text interpolation (under a feature flag)	!142009 (merged)
Create feature flag issue for next steps	#435177 (closed)