[BUGFIX] add template name to debug render tree

[chancancode]

I'm not sure if this should be [BUGFIX beta] or [BUGFIX release]?

[chancancode]

Turns out this is not valid: #18547

[rwjblue]

LGTM, let’s call it BUGFIX release..

[rwjblue]

CI failure is due to linting:

yarn run v1.19.1
277$ yarn lint:tsc && yarn lint:tslint && yarn lint:eslint && yarn lint:docs
278$ tsc --noEmit
279packages/@ember/-internals/glimmer/lib/component-managers/input.ts(10,1): error TS6133: 'templateName' is declared but its value is never read.
280packages/@ember/-internals/glimmer/lib/component-managers/input.ts(10,10): error TS2305: Module '"../template"' has no exported member 'name'.
281packages/@ember/-internals/glimmer/lib/component-managers/root.ts(17,1): error TS6133: 'template' is declared but its value is never read.