Pending nodes

[kazcw]

Pull Request Description

Implement pending node status (#7435).

Design reference:
https://user-images.githubusercontent.com/3919101/257222729-838cfe84-7447-40a3-8aa1-5424de66b0b7.png

Demo:
vokoscreenNG-2023-08-09_22-29-13.webm

Important Notes

• Reduce alpha value of node backgrounds, label widgets, and method widget icons while the engine reports "pending" state.
• Use FRP and themes for method widgets.
• Update node input area to use define_endpoints_2.
• Also remove some code supporting the disused profiling mode.

Checklist

Please ensure that the following checklist has been satisfied before submitting the PR:

• The documentation has been updated, if necessary.
• Screenshots/screencasts have been attached, if there are any visual changes. For interactive or animated visual changes, a screencast is preferred.
• All code follows the
  Scala,
  Java,
  and
  Rust
  style guides. In case you are using a language not listed above, follow the Rust style guide.
• All code has been tested:
  • Unit tests have been written where possible.
  • If GUI codebase was changed, the GUI was tested when built using ./run ide build.

[farmaazon]

LGTM, but I'd like to have widget's code checked by @Frizi

[Frizi]

Overall looks good, just some minor stylistic nits.

[MichaelMauderer]

QA: 🟡

This is not clearly defined in the reference design, but with the current implementation, I can see the edges going under the transparent nodes:

This looks weird and unintentional.

[kazcw]

QA: yellow_circle

This is not clearly defined in the reference design, but with the current implementation, I can see the edges going under the transparent nodes:

This looks weird and unintentional.

I've adjusted this at the input port (target attachment) ends, however I can't make the output edges look right by changing their end points, since a flat-ended line can't meet a rounded node exactly. Our current rendering system cannot reconcile performance (minimizing shader count) with transparency. When we eventually switch to Z-buffer compositing, we can draw this correctly.