Boost hashing performance with Robin Hood

[WSLUser]

Description of the new feature/enhancement

Use MIT-licensed https://github.com/martinus/robin-hood-hashing to improve performance and increase memory efficiency. It does come with a custom allocator but it won't win any medals and can be ignored. Instead mimalloc should be compiled in instead and is even recommended by maintainer to use a dedicated allocator instead. This is filed under another issue. Idea for adding this stems from #10521 (comment). Also see #10341 which addressed a bug with hashing that likely will need to be refactored slightly when adopting this library.

Proposed technical implementation details (optional)

Replace use of std::unordered_map and/or std::unordered_set with Robin Hood equivalent among other changes.

[lhecker]

I already have a branch for this: https://github.com/microsoft/terminal/tree/dev/lhecker%2Frobin-hood-hashing
It results in a rather significant binary size increase and doesn't make any noticeable performance differences. It does however improve memory usage significantly under certain conditions.

I'm expecting to introduce that project in a later PR for a purpose were it has a true impact.

[lhecker]

I ended up writing my own purpose built hashmap and won't need martinus/robin-hood-hashing anymore. In other areas of this application hashmaps aren't used much.