SI-7649 Fix positions for reshaped tag materializers

Calls to `materializeClassTag[T]` are replaced during reification with
`implicitly[ClassTag[T]]` in the `reify` macro. This is done to avoid
referring to symbols in scala-compiler.jar. Class- and Type-Tag
materialization is treated in the same way.

This commit positions the replacement trees to avoid triggering
assertions under -Yrangepos.
SI-7649 Refactor materializer reshaping in reification

Minor duplication removal.