Column selection mode: shift selection and move should start from current position

[octref]

Testing #91249:

Let's say I have:

foo|bar

When I do:

• Cmd + Shift + Right
• It selects bar
• Shift + Left
• It selects ba, with cursor in fooba|r

Now do this in column selection mode, the selection is o 🐛

If I only do Shift + Left/Right this seems to work fine. But after Cmd + Shift + Left/Right my Shift + Left/Right moves from the anchor position not the active position.