[SAoC] Move semantics and STL containers

[Suleyman]

This marks the end of milestone 2 for which the objective was to 
implement user controlled move semantics in D.

Accomplished tasks:
- Implementation of the move constructor and move opAssign using 
rvalue ref or alternatively using the @move attribute.
- Fixing most cases of issue 20321 where the compiler copies 
objects without calling the copy or move constructor.

The following tasks will be continued after the SAOC period 
because they didn't fit the schedule of this milestone.
- Implement move semantics in druntime functions that perform 
array operations.
- Solve the two remaining cases of issue 20321.