Draft: Use custom xaxes for 1D data

Closes #2683 (closed)

This is a draft to support custom xaxis for 1D data in Flint.

• provide xaxis meta to scan_info/channels/
• or scan_info/channels/info (place to hold channel info dict)
• update channel info metadata
• Split widget for MCAs, Any 1D, maybe others
  • There is 3 kind of 1D data right now: MCA, ROI profiles, sampling counter in STATS mode
  • There is 2 kind of 2D data, images and stack of curves
• Handle properly MCAs gains (allow to enable/disable it)
• Handle properly xaxis/normalization/label meta in any 1D widget

But other PR have to be done before (#2687 (closed) ):

• It would be good to rework the scan_info in order to distinguish few devices like MCAs
• It would be good to find a way to expose channel info to Flint
  • Add extra event during the data reception (after new child and before any data)
  • Store channel infos inside the scan info
    • Which is i think the best solution, cause it simplify a lot the data reception