Replace RF component selector with new type

[joeyballentine]

Follow up to #2490

Unfortunately, the RF node types aren't type-safe yet, but they will be in v12 (i think).

All this does is finish decoupling the RF node types from the node kinds, and replaces them with just a generic "backendNode" node type which uses our Node component.

[joeyballentine]

This needs a migration... will do in a sec

[RunDevelopment]

You just activated my trap card or something.

Anyway, we still have a bunch of code that uses node.type to get the node kind. You broke all of that, and since node.type is typed as string there aren't compiler errors. Fun. I would suggest using VSCode's "Find All References" to find all uses of .type.

I know this because I investigated this while doing #2490, but I didn't make this change in this PR, because it seemed like it should be its own PR. Well, I guess that PR is right now :)

[joeyballentine]

Hmm, I think I'll just close this and wait til we update to RF v12 to make this change, so that it will actually be typed correctly

[RunDevelopment]

You can also keep it open. I'm gonna work on #2266 tomorrow and I'll change most of the code using node.type. So you'll only have to fix maybe one or two occurrences after that.