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 change positions the replacement trees to avoid triggering
assertions under -Yrangepos.

Review by @xeno-by.

Are we in a better shape to address this problem properly in master?

```scala
// when implicit macros are fixed, these sneaky macros will move to corresponding companion objects
// of, say, ClassTag or TypeTag
```