Revert "[vm/bytecode] Enable bytecode compiler by default in Dart SDK"

This reverts commit 31996aa.

Reason for revert: bytecode mode is disabled to avoid gaps in testing of AST-based mode.

Original change's description:
> [vm/bytecode] Enable bytecode compiler by default in Dart SDK
> 
> This is the reland of https://dart-review.googlesource.com/c/sdk/+/110551.
> 
> Change-Id: I85fcfadfd20fdba752fa8225650a1cb6c32fff31
> Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/117931
> Reviewed-by: Régis Crelier <regis@google.com>
> Commit-Queue: Alexander Markov <alexmarkov@google.com>

TBR=rmacnak@google.com,alexmarkov@google.com,asiva@google.com,regis@google.com

# Not skipping CQ checks because original CL landed > 1 day ago.

Change-Id: I941eff705b599c59251e5ba2337c307cc84f373b
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/120720
Reviewed-by: Alexander Markov <alexmarkov@google.com>
Reviewed-by: Ryan Macnak <rmacnak@google.com>
Reviewed-by: Régis Crelier <regis@google.com>
Commit-Queue: Alexander Markov <alexmarkov@google.com>

Author: alexmarkov

runtime/runtime_args.gni

@@ -80,8 +80,8 @@ declare_args() {
     dart_component_kind = "static_library"
   }
 
-  # Controls whether the VM uses bytecode.
-  dart_platform_bytecode = true
+  # Whether the VM's platform dill file contains bytecode.
+  dart_platform_bytecode = false
 
   # Whether the VM includes the kernel service in all modes (debug, release,
   # product).

tools/gn.py

@@ -428,14 +428,9 @@ def parse_args(args):
     other_group.add_argument(
         '--bytecode',
         '-b',
-        help='Use bytecode in Dart VM',
-        default=True,
+        help='Include bytecode in the VMs platform dill',
+        default=False,
         action="store_true")
-    other_group.add_argument(
-        '--no-bytecode',
-        help='Disable bytecode in Dart VM',
-        dest='bytecode',
-        action="store_false")
     other_group.add_argument(
         '--clang', help='Use Clang', default=True, action='store_true')
     other_group.add_argument(