Increase # of tables threshold in flatbuffer verifier

We were able to encounter AOS configs that exceeded this threshold...

Change-Id: Iac5fe8b2d671d82775701a255f9fee94f9326ff8
Signed-off-by: James Kuszmaul <james.kuszmaul@bluerivertech.com>
diff --git a/aos/config_flattener.cc b/aos/config_flattener.cc
index 5bd3cf7..b089d24 100644
--- a/aos/config_flattener.cc
+++ b/aos/config_flattener.cc
@@ -45,7 +45,9 @@
   aos::FlatbufferDetachedBuffer<Configuration> merged_config =
       configuration::MergeConfiguration(config, schemas);
   // In case we've done something overly weird to the flatbuffer...
-  CHECK(merged_config.Verify());
+  CHECK(merged_config.Verify())
+      << ": Failed to verify flatbuffer. NOTE: Very large flatbuffers could be "
+         "exceeding max_tables in flatbuffers::Verifier.";
 
   const std::string merged_config_json =
       FlatbufferToJson(&merged_config.message(), {.multi_line = true});
diff --git a/third_party/flatbuffers/include/flatbuffers/verifier.h b/third_party/flatbuffers/include/flatbuffers/verifier.h
index 87d3f54..bdc6f36 100644
--- a/third_party/flatbuffers/include/flatbuffers/verifier.h
+++ b/third_party/flatbuffers/include/flatbuffers/verifier.h
@@ -25,11 +25,13 @@
 // Helper class to verify the integrity of a FlatBuffer
 class Verifier FLATBUFFERS_FINAL_CLASS {
  public:
+  static constexpr uoffset_t kDefaultMaxTables = 3000000;
+
   struct Options {
     // The maximum nesting of tables and vectors before we call it invalid.
     uoffset_t max_depth = 64;
     // The maximum number of tables we will verify before we call it invalid.
-    uoffset_t max_tables = 1000000;
+    uoffset_t max_tables = kDefaultMaxTables;
     // If true, verify all data is aligned.
     bool check_alignment = true;
     // If true, run verifier on nested flatbuffers
@@ -44,7 +46,8 @@
 
   // Deprecated API, please construct with Verifier::Options.
   Verifier(const uint8_t *const buf, const size_t buf_len,
-           const uoffset_t max_depth = 64, const uoffset_t max_tables = 1000000,
+           const uoffset_t max_depth = 64,
+           const uoffset_t max_tables = kDefaultMaxTables,
            const bool check_alignment = true)
       : Verifier(buf, buf_len, [&] {
           Options opts;