Statprof uses stack trace buffer to always provide full stacks

Statprof uses stack trace buffer to always provide full stacks

* module/statprof.scm (<state>): Remove record-full-stacks? and stacks
  members.  The stack trace buffer is sufficient.
  (fresh-profiler-state): Adapt.
  (sample-stack-procs): Don't save stacks.
  (statprof-reset): Deprecate the full-stacks? argument.
  (stack-samples->procedure-data): Remove a needless vector-ref.
  (stack-samples->callee-lists): New helper.
  (statprof-fetch-stacks): Use stack-samples->callee-lists.
  (statprof-fetch-call-tree): Use stack-samples->callee-lists, and
  implement our own callee->string helper.
  (statprof, with-statprof, gcprof): Deprecate full-stacks? argument.