Naming convention: don't pun serial type names

[dherman]

NOTE: this issue predates this project's rename to Volta.

As @mikrostew pointed out in #221, it's confusing to have foo::Bar and foo::serial::Bar types have the same name, especially with foo::serial::Bar::into_bar().

Example: notion_core::inventory::NodeIndex and notion_core::inventory::serial::NodeIndex.

Some possible naming conventions:

• notion_core::inventory::serial::NodeIndexAst (i.e., AST)
• notion_core::inventory::serial::NodeIndexIr (i.e., IR)
• notion_core::inventory::serial::NodeIndexSerial
• notion_core::inventory::serial::NodeIndexSerde
• notion_core::inventory::serial::NodeIndexSD
• notion_core::inventory::serial::SerialNodeIndex
• notion_core::inventory::serial::SerdeNodeIndex
• notion_core::inventory::serial::SDNodeIndex

I don't love any of these. Other ideas?

[charlespierce]

Looking at some (de)serialization stuff for the package configs, I wonder if the solution would actually be to not have "serial types" at all. From what I can tell, we should be able to serialize / deserialize directly to / from the actual data models used in Volta.

That way we avoid needing to parse into an intermediate type, then convert that type to our data model (and the reverse when writing).