Edit existing wishes on their page, via ?wishedit=1

Rather than putting the wish slug in the wishedt URL param and using the /Intake subpage for editing as well as creating, this switches to staying on the wish page for editing and changing that URL parameter to a boolean.

This is in order to fix the edit, history, and toolbox links that use the page title, so that it's not the /Intake subpage that's used for these.

Bug: T367845