Change reroute behaviour on trimmed paths

[lewri]

Fixes #2501

Describe what the proposed change does

• Adds a new parameter to the Walk action where a trimmed path issued
• Instead of attempting a reroute inside the Walk, the action is finished instead
• In the case of SeekReception, that action calls a new Walk with an updated path.

@Alberth289346 and I discussed this one, and both agree currently there may not be a very nice way to do this, but as it's a regression of #1852 introduced in 0.67 it may be worth considering a fix for now. A better long term solution is recoding how walk is handled as a whole.

[Alberth289346]

I like the solution, good work !

[lewri]

Not sure if @mugmuggy is about but his input would be nice to know too before making this ready.