Potential 1.15 performance regression

Our [benchmarks](https://benchs.haxe.org/allBenchmarks.html#1;false;true;true;DataAndAverage;SMA;2025-03-12;;HashLink;runtime) show a performance regression starting on March 23rd, which coincides with the 1.15 release. This applies to both Haxe nightlies and Haxe 4, and affects both HL/JIT and HL/C.

It's particularly bad for the allocation-bound benchmarks like mandelbrot, but some normal ones like the formatter also took a hit. The only one that got better is the Dox benchmark, which suggests some improvement related to dynamic field handling or something along those lines.

@Apprentice-Alchemist mentioned that the benchmarks went from HL 1.13 to 1.15, so this might be an older regression introduced in 1.14.