ENH: New interface for Coregistration

• increase fiducial picking performance (https://github.com/mne-tools/mne-python/pull/9689#issuecomment-951910957)
• add support for the project_eeg parameter
• add support for the scale_by_distance parameter
• add support for the mark_inside parameter
• console/status_bar idea to add to the UI whatever is printed in the terminal
• display dist estimation in mm.
• add units to UI (Omit more explicit message)
• display axes
• add tooltips as much as possible on widgets
• add support for the scaling parameters (https://github.com/mne-tools/mne-python/pull/10117)

Bonus territory:

• checkbox for the MEG helmet
• add a slider to control transparency
• add a button to save the fiducials (https://github.com/mne-tools/mne-python/issues/10208#issuecomment-1016402749)
• rename "Transform" groupbox into "HEAD <> MRI Transform"
• find a better name for the "Digitization Source" section (which could be confusing)
• show a dialog to save if trans is not saved (https://github.com/mne-tools/mne-python/issues/10236)
• add a prompt check name already exists "overwrite or not"

• add legend to plot alignment / coreg to see what colored points are etc.
• add support for (qdarkstyle) dark theme
• 📁 icon for file button widgets (instead of "Load")
• multiple threads should block window exit
• add support for object_fit='contain' and object_position='top' (ipywidgets) (https://github.com/Kitware/ipyvtklink/issues/35, https://github.com/mwcraig/ipyevents/issues/71)

• add support for the guess_mri_subject parameter (YAGNI)
• add support for the head_inside parameter (YAGNI)
• Update Coregistration() to require parameters (https://mne.discourse.group/t/mne-coreg-based-on-ctf-data/3022/4)
• make the sections collapsible (ipywidgets)
• Decouple GUI code from model (suggested in https://github.com/mne-tools/mne-python/pull/6693#issuecomment-542364434, done in https://github.com/mne-tools/mne-python/pull/9516)
• Build a coreg GUI using pyvista (done in https://github.com/mne-tools/mne-python/pull/9689)

• the parameter spin boxes force 2 updates consecutively even though only one interaction is done
• multi-line labels are not supported (ipywidgets)
• Qt crashes during _configure_status_bar() (Windows)
• the app is abnormally slow at loading FIFF (Windows)
• inconsistent behaviour of checkbox layout (ipywidgets)
• the status bar does not support dark theme (qt) (https://github.com/mne-tools/mne-python/pull/10238#issuecomment-1079155443)
• the spin boxes are not updated during ICP with scaling (https://github.com/mne-tools/mne-python/pull/10377#issuecomment-1061901037)
• the DigPoints are displayed with unlocked fiducials when switching subjects (https://github.com/mne-tools/mne-python/pull/10242#issuecomment-1023977033)
• all HSPs become marked as inside the head surface on certain scaling values (https://github.com/mne-tools/mne-python/pull/10224#issuecomment-1017592043)
• the app hangs when loading trans (ipywidgets)