* Removed unneeded headers
This removes some unneeded headers from the headers.
* Remove use of std::string
This stack allocates and copies a c-string to replace the calls to std::string.
In test/perf/startup, gcc (Debian 14.2.0-3) seems to get confused about
the size of the counters vector as the code was written. Rewrite the
code to pass the same value (`std::thread::hardware_concurrency()`, but
in a local) to both `counters.resize()` and the `ParallelTest` ctor.
* Benchmark for testing startup performance.
* Make pool pass spare space to pooled item
The pool will result in power of 2 allocations as it doesn't have a
local state when it is initially set up.
This commit passes this extra space to the constructor of the pooled
type, so that it can be feed into the freshly created allocator.
Co-authored-by: Nathaniel Wesley Filardo <nfilardo@microsoft.com>