Optimize Path3DGizmo mesh generation

[BlueCube3310]

Optimizes the way Path3d editor preview meshes are generated by avoiding unnecessary reallocations and COW, as suggested by AThousandShips in #83698 (comment).

Also fixes a bug where the function would reach outside of the frames array when generating _collision_segments.

The function itself is bottlenecked mainly by the sample_baked function and as such the resulting times vary between 3.5s and 5.0s.

As for the changes with the modified part of the function:
Build: editor x64 --production=yes & debug_symbols=yes

Path3D with baked length of 26744.5:

master	PR
0.03s	0.005s

[clayjohn]

How much did performance improve in your tests?

[BlueCube3310]

After experimenting more with the --production build, the modified part of the function seems to perform about 5-6 times faster. The redraw function as a whole yields heavily varying results, as no matter which build is tested (master or this PR) the time takes between 3.5 and 5.0 seconds.

[fire]

Let us know when this is ready for review.

[BlueCube3310]

It's ready now.
I also feel like it's worth mentioning that the performance difference is most significant on older CPUs, while on the most modern ones it's not particularily noticeable.

[Calinou]

Tested locally, it works as expected (gizmo appearance is identical to before, and editing the gizmo still looks correct).

[clayjohn]

Looks great! Thanks for following up

[YuriSizov]

Thanks!