#2584 #2750 - Selection tool: add flip and delete buttons & Rotation Tool: non-selected end of the selected bond should be the rotation center

[yuleicul]

Closes #2584
Closes #2750

What's new

Floating buttons

• add new floating buttons for flipping and deleting structures.
• remove rotate tool, horizontal flip tool, and vertical flip tool from the left toolbar
• remove rotation's shortcut alt+r
• delete rotation icon from codebase

New flip support

• Support flipping multiple structures as a whole
• Support flipping reaction arrows, pluses, and texts

more details:

[KonstantinEpam23]

After merging #2680 into this branch, another issue occurs:
At this moment, arrows are not allowed to flip
I propose to: support flipping arrows in the scope of this pull request OR disable flipping buttons for arrows (and maybe create a new issue to support flipping)

Hi @yuleicul! I believe we do need to support flipping arrows for reactions (especially since we already support rotating them)
Flipping arrow by itself is probably a rare usecase, but if there are other structures in the selection - we cant disable the flip buttons and it might be confusing for the user if the arrows dont flip.

I would propose to support flipping arrows in the scope of this pull request, unless it is hard to implement.

[kaluginserg]

@yuleicul thanks for your work, it is a good solution.
I saw you've started working on additional functionality for choosing the rotation center....
Could we please do it in a separate PR?
It is not a good practice to have long-live PRs and also it is not a good practice to have PR with various changes.
Why? Using small pull requests can lead to more efficient code reviews, faster feedback, fewer merge conflicts, and a more stable and maintainable codebase.

[yuleicul]

@kaluginserg Thanks for your review! Actually, the reason why I close two issues in this PR is because the two issues have overlapped code, if I open separate PRs, it may be hard to resolve conflicts.

But anyway, thanks for your kind reminder, I'll pay more attention next time.