Particle trail setup is clunky and has redundant configuration

[QbieShay]

Godot version

4.0 stable

System information

Fedora, RX 590

Issue description

Opening as an issue, because I think it's a usability issue.

Setting up trails is currently very complicated and there's only a handful of confiugurations, out of the possible ones on particles + particle material + trails that actually make them work.

Furthermore, the transform align properties are really useful but they could be unified with the billboard modes in the billboard node, since they cover similar usecases ("how should this item orient?").

My current way of working with all of this is to ditch the built-in options and implement my own in the shader, because they're just too scattered to work with in a consistent manner.

Steps to reproduce

I have struggled to navigate this issue because there's a lot of options I don't understand and I am not sure which options should work with which option. What i know I use, as a VFX artist, are the following things:

1. Ribbon style billboarding: like y billboard, but on the y axis of the particle instead of the global y axis
2. Velocity aligned billboard: the particle is billboarded, but the angle is not determined by the angle properties but rather the angle that the Y axis of the particle has on screen. So my shader substitutes that in the rendering stage with the INSTANCE_CUSTOM.x properties, and uses regular particle billboard code after that
3. Ribbon trails, which is what the pipeline is configured for.

Minimal reproduction project

See above