add gdb, strace to workbench Dockerfile

[kevinushey]

Closes #891.
Maybe also #887?

I'm also not sure if I'm targeting the correct Dockerfiles 😅 The goal is to have the session images at https://dev.palm.ptd.posit.it updated.

[cm421]

This would technically work, though I suspect a more appropriate location would be in the base image package list. That would extend gdb and strace to all of the product images.

That's a very unilateral decision, however, which would likely start a lengthy back-and-forth discussion across all the teams. We can put it here for now, but given there's another issue making this request, we should at least start the conversation in the meantime, unless @ianpittwood or @bschwedler would rather we put this in the base image?

[cm421]

Approving for now. If other teams are open to including it we can move it into the base or pro images later