No more VM objects visible to Scheme

No more VM objects visible to Scheme

* libguile/vm.h:
* libguile/vm.c (scm_the_vm): Don't expose to Scheme.
  (scm_vm_p): Remove, as it is not needed.

* module/system/vm/vm.scm: Remove the-vm and vm? exports.

* doc/ref/api-coverage.texi (Code Coverage):
* test-suite/tests/coverage.test:
* module/system/vm/coverage.scm (with-code-coverage): Don't take a VM
  argument.  Adapt documentation and tests.

* module/ice-9/command-line.scm: Remove the-vm autoload.

* module/system/vm/trace.scm (trace-calls-to-procedure):
  (trace-calls-in-procedure):
  (trace-instructions-in-procedure):
  (call-with-trace): Remove #:vm kwarg, and adapt to trap changes.

* module/system/vm/trap-state.scm (the-trap-state): Rework to use a
  parameter underneath instead of a weak key on (the-vm).

* module/system/vm/traps.scm (new-disabled-trap):
  (new-enabled-trap): Remove vm argument.
  (trap-at-procedure-call):
  (trap-in-procedure):
  (trap-instructions-in-procedure):
  (trap-at-procedure-ip-in-range):
  (trap-at-source-location):
  (trap-frame-finish):
  (trap-in-dynamic-extent):
  (trap-calls-in-dynamic-extent):
  (trap-instructions-in-dynamic-extent):
  (trap-calls-to-procedure):
  (trap-matching-instructions): Remove vm keyword arguments.

* test-suite/tests/control.test ("unwind"): Adapt test.

* test-suite/tests/eval.test (test-suite): Remove the-vm import.