Do not configure non-template rst files

Summary

CMAke documentation is stored in .rst files. Those files are copied from the source tree into the build/install tree. If it is configured instead, some special placeholders and some special symbols are replaced. This is wanted for template files, typically called .rst.in, but not necessarily for regular documentation files that might even contain commands that would be replaced in a configure step but should not.

This MR does a copy only instead of a full configure of .rst files, those that are not named like templates. See !1262 (merged) for an issue with the old approach.