v4 - Remove Tether for Popper

Created by: Johann-S

Remove Tether for Popper

Reasons

• @FezVrasta and his community are very active
• Popper fix a lot of bug that Tether didn't handle (see listed issues below)
• Tether recommand the use of Popper.js

TODO

• Stop using Tether for Tooltip, Popover
• Use Popper for Dropdown
• Check dropup for Dropdown
• Fix unit test (#22464)
• Remove Tether as a dependency
• Add update method to update position for Tooltip/Popover/Dropdown
• Add flip attribute for Dropdown to disable the flip behavior of Popper.js
• Add fallbackPlacement for Tooltip and Popovers
• Update documentation
  • Remove Tether
  • Add that Dropdown now depend on Popper
  • Add offset option in documentation for Dropdown

Work in progress...

Close : #19685 (closed), #19279 (closed), #22261 (closed), #22249 (closed), #22022 (closed), #21962 (closed), #19888 (closed), #17167 (closed), #17669 (closed)