deps: cherry-pick 26b145a from upstream V8

Original commit message:

    [api] Deprecate ExternalStringResourceBase::IsCompressible

    R=yangguo@chromium.org

    Bug: v8:8238
    Change-Id: Ia59aefc54c2e9f4fa3348c42fb45e7fadab8ee76
    Reviewed-on: https://chromium-review.googlesource.com/c/1349231
    Reviewed-by: Yang Guo <yangguo@chromium.org>
    Commit-Queue: Andreas Haas <ahaas@chromium.org>
    Cr-Commit-Position: refs/heads/master@{#57788}

Refs: v8/v8@26b145a

common.gypi

@@ -38,7 +38,7 @@
 
     # 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.7',
+    'v8_embedder_string': '-node.8',
 
     ##### V8 defaults for Node.js #####
 

deps/v8/include/v8.h

@@ -2631,8 +2631,7 @@ class V8_EXPORT String : public Name {
    public:
     virtual ~ExternalStringResourceBase() = default;
 
-    V8_DEPRECATE_SOON("Use IsCacheable().",
-                      virtual bool IsCompressible() const) {
+    V8_DEPRECATED("Use IsCacheable().", virtual bool IsCompressible() const) {
       return false;
     }
 
@@ -2641,16 +2640,7 @@ class V8_EXPORT String : public Name {
      * ExternalStringResource::data() may be cached, otherwise it is not
      * expected to be stable beyond the current top-level task.
      */
-    virtual bool IsCacheable() const {
-#if __clang__
-#pragma clang diagnostic push
-#pragma clang diagnostic ignored "-Wdeprecated-declarations"
-#endif
-      return !IsCompressible();
-#if __clang__
-#pragma clang diagnostic pop
-#endif
-    }
+    virtual bool IsCacheable() const { return true; }
 
    protected:
     ExternalStringResourceBase() = default;