[SAoC] Move semantics and STL containers

[Suleyman]

Week 1 status:
     - `@rvalue ref` attribute fully implemented[1]
       - grammar definition[2]
       - parameter and return semantics
       - D and C++ name mangling
       - `cast(@rvalue ref)` to convert lvalues to rvalue ref
       - `__traits(isRvalueRef)` for parameters
       - fully functional with ctfe, inliner, optimizer, codgen
       - escape analysis is the same as `ref`

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[1] https://github.com/dlang/dmd/pull/10426
[2] https://github.com/dlang/dlang.org/pull/2703