The current "Select Linked" operator works based on mouse position and
makes no sense to call from the menus and was removed in rB536055e1ee0b.
This patch adds an operator independent from mouse position that just
selects all bones in relation to selected bones (and adds back menu
entries, adds keymap entry CTRL+L).
The original operator is renamed to 'select_linked_pick' internally
(this is now more in line to how "Select Linked" works for meshes,
curves etc)
ref T76071
Maniphest Tasks: T76071
Differential Revision: https://developer.blender.org/D7542
e07b245fe1