contributing docs: symbols need package prefix; changed allocStats to nimAllocStats (#13247)

tests/destructor/tbintree2.nim

@@ -1,5 +1,5 @@
 discard """
-  cmd: '''nim c -d:allocStats --newruntime $file'''
+  cmd: '''nim c -d:nimAllocStats --newruntime $file'''
   output: '''0
 (allocCount: 6, deallocCount: 6)'''
 """

tests/destructor/tgcdestructors.nim

@@ -1,5 +1,5 @@
 discard """
-  cmd: '''nim c -d:allocStats --newruntime $file'''
+  cmd: '''nim c -d:nimAllocStats --newruntime $file'''
   output: '''hi
 ho
 ha

tests/destructor/tnewruntime_misc.nim

@@ -1,5 +1,5 @@
 discard """
-  cmd: '''nim cpp -d:allocStats --newruntime --threads:on $file'''
+  cmd: '''nim cpp -d:nimAllocStats --newruntime --threads:on $file'''
   output: '''(field: "value")
 Indeed
 axc

tests/destructor/tnewruntime_strutils.nim

@@ -1,6 +1,6 @@
 discard """
   valgrind: true
-  cmd: '''nim c -d:allocStats --newruntime -d:useMalloc $file'''
+  cmd: '''nim c -d:nimAllocStats --newruntime -d:useMalloc $file'''
   output: '''
 @[(input: @["KXSC", "BGMC"]), (input: @["PXFX"]), (input: @["WXRQ", "ZSCZD"])]'''
 """

tests/destructor/tsimpleclosure.nim

@@ -1,5 +1,5 @@
 discard """
-  cmd: '''nim c -d:allocStats --newruntime $file'''
+  cmd: '''nim c -d:nimAllocStats --newruntime $file'''
   output: '''a b
 70
 hello

tests/destructor/tv2_raise.nim

@@ -1,6 +1,6 @@
 discard """
   valgrind: true
-  cmd: '''nim c -d:allocStats --newruntime $file'''
+  cmd: '''nim c -d:nimAllocStats --newruntime $file'''
   output: '''OK 3
 (allocCount: 8, deallocCount: 3)'''
 """

tests/destructor/twidgets.nim

@@ -1,5 +1,5 @@
 discard """
-  cmd: '''nim c -d:allocstats --newruntime $file'''
+  cmd: '''nim c -d:nimAllocStats --newruntime $file'''
   output: '''button
 clicked!
 (allocCount: 4, deallocCount: 4)'''

tests/destructor/twidgets_unown.nim

@@ -1,5 +1,5 @@
 discard """
-  cmd: '''nim c -d:allocStats --newruntime $file'''
+  cmd: '''nim c -d:nimAllocStats --newruntime $file'''
   output: '''button
 clicked!
 (allocCount: 9, deallocCount: 9)'''