Rename {selection-text} to {popup-selection-text}

[khaitruong922]

#1062

• Add a field called popup-selection-text to return the same value as selection-text.
• Remove selection-text from the selection.
• Migrate new naming to Anki templates and Chrome settings.

[StefanVukovic99]

I think instead of modifying older handlebars updates this should have a new handlebars update 45 that renames selection text, and an upgrade version function in options util that updates references in existing anki settings.

SelectionText type and variables should also be renamed i guess.

The only mentions of the unprefixed selection-text left would be in the handlebars updates (13, 33, and the new 45), and in the new _updateVersion45.