Dragging a FG on a FG connected to an atom make overlap instead of replace

[Zhirnoff]

Steps to Reproduce

1. Open Ketcher
2. Add Functional Group connected with atom on canvas
3. Select another Functional Group and add to canvas
4. Choose 'Selection tool' and drag FG to Functional Group connected with atom and try to connect to FG
5. Choose 'Selection tool' and drag FG to Functional Group connected with atom and try to connect to atom

Actual behavior

1. Connection to Functional Group: FG overlap FG
2. Connection to atom: Two functional groups are formed after connection to atom. Sometimes four
   Note: Pay attention to the highlight of the atoms and bond - they start to glow when the FG is just brought up to them

Expected behavior

1. Connection to Functional Group: FG replace FG
2. Connection to atom: FG replace atom
   Note: Pay attention to the highlight of the atoms and bond - they start to glow when the FG is just brought up to them

Screenshots

2023-02-23_19h52_52.mp4

Desktop (please complete the following information):

• OS: Windows 10
• Browser Chrome
• Version 109.0.5414.120 (Official Build) (64-bit)

Ketcher version
Version 2.8.0-rc.4

[yuleicul]

A note: merging behaviors are different after several undo. See: #2302