Merge branch '415811-replace-context-switcher' into 'master'

Replace context switcher with header in sidebar

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/129843



Merged-by: Mayra Cabrera <mcabrera@gitlab.com>
Approved-by: Thomas Hutterer <thutterer@gitlab.com>
Approved-by: Austin Regnery <aregnery@gitlab.com>
Approved-by: Lukas 'Eipi' Eipert <leipert@gitlab.com>
Approved-by: Mayra Cabrera <mcabrera@gitlab.com>
Reviewed-by: Mayra Cabrera <mcabrera@gitlab.com>
Reviewed-by: Lukas 'Eipi' Eipert <leipert@gitlab.com>
Reviewed-by: Mark Florian <mflorian@gitlab.com>
Co-authored-by: Lukas Eipert <leipert@gitlab.com>
Co-authored-by: Mark Florian <mflorian@gitlab.com>
Co-authored-by: Sanad Liaquat <sliaquat@gitlab.com>