Flint: Improve sequence support

This MR allow to display plots for scan sequences + few scatters improvements

Related to #1858 (closed)

• Flint
  • When a ScanGroup contains a scan_info["type"] it is considered as a displayable scan for Flint
    • Other metadata like scan_info["acquisition_chain"] must be set properly.
    • In this case the sub scans will not be displayed.
  • If no metadata are provided to scatters, it is not considered as displayable like an image
• BLISS
  • scan_info description updated
  • Added bliss.common.scans.scan_info.ScanInfoBuilder to help to custom scan_info content
  • Scatter plot can be explicitly defined
  • Channels can be grouped together, as result there size and structure are supposed to be the same
  • New axis kind fast-backnforth was added
    • amesh was updated to use it
  • scan_info["group"] can be defined for scans part of a scan group.
    • It is automatically set for not-yet-running scans added to a sequence
  • watch_scan_group can emit callback for scan groups

Demo

Can be tested this way with the demo_session

flint()
import os
userscripts = os.path.join(os.getcwd(), "demo", "userscripts")
user_script_homedir(userscripts)
tomo = user_script_load("tomo.py", export_global=False)
tomo.fullfield_tomo(demo_session, expo=0.01)