Use the position of the Context Menu as the center when zoom in & zoom out

[iannbing]

Description

Currently, Zoom in and Zoom out in the Context Menu assume the center point of the canvas as the center.
This PR makes it so that it will zoom in/out precisely with the position of the Context Menu.

This PR also fixes another minor issue:
When zoom in/out with pinching, the speed of zoom in/out is consistent; sometimes it becomes faster and faster (or slower and slower). This PR makes it consistent and smooth.

Checklist

• The PR branch is set up to merge into dev instead of master.
• I haven't introduced breaking changes that would disrupt existing jobs, i.e. backwards compatibility is maintained.
• In case I changed the dependencies in any requirements.in I have run pip-compile to update the corresponding requirements.txt.
• In case I changed one of the services' models.py I have performed the appropriate database migrations (refer to the DB migration docs).
• In case I changed code in the orchest-sdk I followed its release checklist.
• In case I changed code in the orchest-cli I followed its release checklist.