Naming: Underscores

[theunrepentantgeek]

What this PR does / why we need it:

To reduce the number of changes in #2084, we want to pull naming changes forward, allowing more meaningful review.

This PR introduces underscores (_) as separators between names when using the access path of a property to generate a custom type name, and updates all affected code.

Key changes are in the generator and the configuration yaml files - everything else flows from those.

Prerequisites

• [ ] Merge #2444
• [ ] Merge #2448

Special notes for your reviewer:

When processing embedded subresources, a cache of all renames made is constructed to allow easy remapping back to the original embedded names.

Identifier factory maintains existing isolated _ separators (but will collapse multiple adjacent underscores together)

AssignProperties methods now have separators to make the direction and target more visible

• AssignProperties_From_Person_Spec
• AssignProperties_To_Person_Spec

CrossPlane now uses the suffix _Parameters to conform with our new standard

Lookup of related types based on the swagger files now ignores _ as well as letter case

TypeTransformer now includes details of the embedded TypeMatcher when an error occurs.

Configuration errors with PropertyTransformers now list all errors, not just the first.

How does this PR make you feel:

If applicable:

• [x] this PR contains tests