fix: address clang-tidy warnings

[Nerixyz]

• Adds /* tag */ to tag argument in tag_invoke
• Removes std::move for (known) trivially copyable types - we have to emulate std::is_trivially_copyable a bit. We have static_asserts to make sure that's actually true
• Uses std::move for vectors (they were copied before)
• Types without members won't create a root variable anymore

Fixes #5913.