Allow Blueprint types to be full Archetype/Components within a scoped namespace

[jleibs]

What

Blueprint code will benefit from being able to leverage the same Archetype / Component patterns as our other datatypes.

Rather than treating Blueprint as an alternative ObjectKind this now uses a blueprint scope for the given blueprint types. This had some obnoxious fan-out to clean up all of the C++ header / include / namespace / python import stuff.

Probably best reviewed commit by commit.

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[teh-cmc]

One oddity in the C++ output but other than that I think this looks as expected. 🥵

[teh-cmc]

⚠️ We're in rerun/blueprint/blueprint, something went wrong... is this some orphaned thing?

[jleibs]

Ahh, yes, that was one of the things that got fixed later in the stack but I failed to commit the removal. Thanks for catching.