Consider using alternatives to standard library types

[SamVanheer]

Consider using alternatives the C++ standard library types.

The following types are known to have performance issues that can be avoided using replacements:

Type	Alternative
unordered_map	See this benchmark for a starting point: https://martin.ankerl.com/2022/08/27/hashmap-bench-01/#benchmark-results-table
regex	Boost.Regex

Make sure to test changes to ensure correctness.