deprecate newruntime (#17245)

* deprecate newruntime
* tests
* Update compiler/commands.nim

doc/advopt.txt

@@ -25,7 +25,6 @@ Runtime checks (see -x):
   --floatChecks:on|off      turn all floating point (NaN/Inf) checks on|off
   --nanChecks:on|off        turn NaN checks on|off
   --infChecks:on|off        turn Inf checks on|off
-  --refChecks:on|off        turn ref checks on|off (only for --newruntime)
 
 Advanced options:
   -o:FILE, --out:FILE       set the output filename

doc/nimc.rst

@@ -431,8 +431,8 @@ Define                   Effect
 ``useMalloc``            Makes Nim use C's `malloc`:idx: instead of Nim's
                          own memory manager, albeit prefixing each allocation with
                          its size to support clearing memory on reallocation.
-                         This only works with ``gc:none`` and
-                         with ``--newruntime``.
+                         This only works with ``gc:none``, ``gc:arc`` and
+                         ``--gc:orc``.
 ``useRealtimeGC``        Enables support of Nim's GC for *soft* realtime
                          systems. See the documentation of the `gc <gc.html>`_
                          for further information.