deps: V8: cherry-pick f6bef09b3b0a

Original commit message:

    [turboshaft] initialize constant_value_ to an empty value

    gcc-10 seems to have a bug were not initializing this value
    throws this compilation error:
    ```
    src/compiler/turboshaft/assembler.h:680:16: error: ‘<anonymous>’ is used uninitialized in this function [-Werror=uninitialized]
      680 |     return Get();
    ```
    https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86465

    Bug: v8:12783
    Change-Id: I7a5fee5009b866a801326fba734c156c3cfdb1b0
    Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/5503350
    Reviewed-by: Nico Hartmann <[email protected]>
    Commit-Queue: Milad Farazmand <[email protected]>
    Cr-Commit-Position: refs/heads/main@{#93675}

Refs: v8/v8@f6bef09
PR-URL: #52802
Fixes: #52661
Reviewed-By: Michaël Zasso <[email protected]>
Reviewed-By: Mohammed Keyvanzadeh <[email protected]>
Reviewed-By: Marco Ippolito <[email protected]>
Reviewed-By: Yagiz Nizipli <[email protected]>

Author: richardlau

common.gypi

@@ -37,7 +37,7 @@
 
     # Reset this number to 0 on major V8 upgrades.
     # Increment by one for each non-official patch applied to deps/v8.
-    'v8_embedder_string': '-node.11',
+    'v8_embedder_string': '-node.12',
 
     ##### V8 defaults for Node.js #####
 

deps/v8/src/compiler/turboshaft/index.h

@@ -480,7 +480,7 @@ class ConstOrV {
   template <typename U,
             typename = std::enable_if_t<std::is_constructible_v<V<T>, V<U>>>>
   ConstOrV(V<U> index)  // NOLINT(runtime/explicit)
-      : constant_value_(), value_(index) {}
+      : constant_value_(std::nullopt), value_(index) {}
 
   bool is_constant() const { return constant_value_.has_value(); }
   constant_type constant_value() const {