The XRC files are inside share\CodeBlocks\resources.zip. You can edit them with any text editor (including Code::Blocks, SciTE, or Notebook).
Submitting a feature request will not avail you, since we will certainly not make this configurable any time soon, but it will be included in the action based event system, anyway. Right now, it is a prohibitive amount of work to change toolbar tooltips programmatically.
On the other hand, the future action-based event handling system generates toolbar buttons programmatically, anyway. Thus, showing shortcuts in tooltips (and making this configurable) comes for free.