Set of improvements: selection "committed" state and "add new compnent" button hitbox fix.

[farmaazon]

Pull Request Description

1. Did selection refactoring as follow-up of Visual way to group components #9519. Now the circular menu visibility or node extension is altered only when selection is ended (before, node shrank once the selection started a bit less blinking).

Screencast.from.2024-04-24.10-56-05.webm

3. Fixes Add component button click zone needs to be bigger #9699 I don't know why the add-node button shape was done in :before element, if it happily works by shaping the main div itself.

Screencast.from.2024-04-24.10-51-57.webm

Important Notes

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.